Royal Army College

Lesson Overview

This is the heart of the course. Beneath all the detail of the law lie four principles a soldier carries into every operation and applies, often in seconds, alone: distinction, proportionality, precautions, and humanity. Master them and you have the working core of the entire law of armed conflict, because almost every rule in the lessons that follow is one of these four worked out in a particular case. This lesson explains each in plain soldier's language, gives each an example, and shows how they balance against military necessity, the lawful need to win, which justifies force but never cruelty.

The four principles are not facts to recall on a test; they are a way of seeing a situation, and that way of seeing must be settled before the situation arrives. So this lesson teaches each as a step a soldier actually takes: how to tell a lawful target from a protected one, how to weigh harm against advantage before a shot is fired, what feasible care looks like in the choice of target, weapon, timing, and warning, and where the line of humanity runs through both the means used and the treatment of those who fall into one's hands. For the Royal Kaharagian Army, a small, lightly armed, humanitarian home-defence force, these principles will live far less often through deliberate attack than through the Rules for the Use of Force that govern home-soil and relief tasks, where the everyday question is not "who may I target" but "when, and how little, may I use force at all." The principles are the same; the setting is gentler, and the care is greater.

By the end you will be able to state and explain the four principles of distinction, proportionality, precautions, and humanity, give a concrete example of each, work a simple "may I engage?" decision aid that runs distinction, then proportionality, then precautions, and explain how military necessity both permits force and is bounded by these principles.

Key Terms

Distinction: the duty to distinguish at all times between combatants and military objectives on the one hand, and civilians and civilian objects on the other, and to direct attacks only at the former.
Military objective: an object that by its nature, location, purpose, or use makes an effective contribution to the enemy's military action, and whose destruction or capture offers a definite military advantage.
Proportionality: the rule that an attack on a lawful target is nonetheless forbidden if the expected incidental harm to civilians and civilian objects would be excessive in relation to the concrete and direct military advantage anticipated.
Incidental harm: the death of or injury to civilians, and damage to civilian objects, expected as a side effect of an attack on a lawful target. Often called collateral damage. It is the harm proportionality weighs.
Precautions: the constant duty to take all feasible care to spare civilians, in the choice of target, means, and timing, and to warn where circumstances permit. It includes precautions against the effects of attacks, the duty to protect the civilians on one's own side.
Feasible: practicable in the circumstances at the time, taking account of all that bears on the situation, including the information available and the risk to the force. Feasible is not "ideal" and not "whatever is convenient"; it is what can genuinely be done.
Direct part in hostilities: an act by a civilian that, for the time it lasts, makes them a lawful target, because it causes harm to the enemy as a direct part of the fighting. The civilian's protection returns the moment the act ends.
Humanity: the principle that forbids means and methods causing superfluous injury or unnecessary suffering, and requires humane treatment of those in one's power.
Superfluous injury or unnecessary suffering: harm to a combatant beyond what is needed to put them out of the fight. The standard by which cruel weapons and methods are judged and banned.
Military necessity: the lawful need to use the force genuinely required to achieve the legitimate aim of the conflict, and no more. It permits force but never licenses cruelty.

Necessity and the four principles

Lesson 01 set out the great balance from which the whole law is drawn: military necessity on one side, the plain need of a force to defeat its enemy, and humanity on the other, the conscience that forbids suffering not needed for that aim. The four principles are how that balance is struck in practice. Necessity is not one of the four; it is the counterweight they are set against. It explains why force is permitted at all, and it is bounded, never unlimited. A soldier may use the degree of lawful force required to achieve the legitimate aim, the submission of the enemy, and nothing beyond it. Necessity justifies the lawful destruction of the enemy's means of fighting; it never justifies cruelty, and it is never an excuse for an act the law forbids.

The four are best seen laid out together before taking them one at a time, because their order is not accidental: each builds on the one before, and the first carries all the rest.

   THE FOUR PRINCIPLES  (military necessity is the counterweight, not one of the four)

   1. DISTINCTION      Who, or what, may I attack at all?
                       -> only combatants and military objectives; never civilians.

   2. PROPORTIONALITY  Even so, is the expected harm to civilians too high
                       for the advantage gained?
                       -> if the incidental harm would be excessive, do not attack.

   3. PRECAUTIONS      What can I do to make that harm smaller before I act?
                       -> verify, choose the least harmful means, time it well, warn.

   4. HUMANITY         By what means, and how do I treat those in my power?
                       -> no cruel weapons; humane treatment of all who are hors de combat.

   Read top to bottom, they answer: may I, should I, how do I, and by what means.

Distinction

Distinction is the cornerstone, the first principle and the one all the others rest upon. At all times, distinguish between those who may be attacked and those who may not, and direct your attacks only at the first. On one side stand combatants and military objectives, the enemy's fighters and the things that make an effective contribution to their military action. On the other stand civilians and civilian objects, the people and the property that take no part in the fighting. Your fire goes only to the first. The civilian population, and individual civilians, must never be made the object of attack.

A military objective is not anything a soldier finds useful to destroy. It is an object that, by its nature, location, purpose, or use, makes a real contribution to the enemy's military action, and whose destruction or capture offers a definite, concrete military advantage in the circumstances of the moment. An enemy gun position is a military objective; a family's home is not. Where there is genuine doubt, the law decides for protection: a person in doubt is presumed to be a civilian, and an object normally used for civilian purposes, a house, a school, a place of worship, is presumed not to be a military objective. Distinction also forbids attacks that cannot tell the two apart, the indiscriminate attack that treats a whole inhabited area as a single target, and it forbids using civilians as a shield to protect what a soldier wishes to keep from attack.

Take the test for a military objective slowly, because it is the part most often got wrong. There are two halves, and both must be true at once. The first half is contribution: the object must make an effective contribution to the enemy's military action, and it can do so in one of four ways. By its nature, a thing military in itself, a weapon, a fighting vehicle, a fortification. By its location, ground that matters militarily, a bridge that carries the enemy's advance, a defile that must be held. By its purpose, the future use the enemy intends for it, a civilian building they are preparing as a strongpoint. Or by its use, what it is being used for now, a school from which the enemy is at this moment firing. The second half is advantage: destroying or capturing it must offer a definite military advantage in the circumstances ruling at the time, not a vague, general, or hoped-for one. A thing it would merely be convenient to destroy, or that might one day matter, is not a military objective. Only when both halves hold, real contribution and definite advantage, may the object be attacked.

   IS THIS OBJECT A LAWFUL TARGET?   Both halves must hold.

   HALF A -- effective contribution to the enemy's military action, by one of:
       Nature    it is military in itself        (a gun, a fighting vehicle)
       Location  the ground itself matters       (a bridge on the enemy's route)
       Purpose   the enemy's intended future use  (a house being prepared as a strongpoint)
       Use       what it is being used for now    (a building fired from right now)

   HALF B -- its destruction or capture offers a DEFINITE military advantage
             in the circumstances at the time (not vague, not "might be useful").

   Both A and B  ->  may be a lawful target.
   Either missing ->  it is a civilian object.  In doubt, presume civilian.

Notice what the test does to the hardest real case, the dual-use object and the place that is ordinarily civilian. A school is a civilian object by its nature. If the enemy fires from it, its present use can make it, for that time, a military objective, but only the part and only the moment the use lasts, and proportionality and precautions still bear on any attack. The instant the use ends, the protection returns. This is why presence is never enough. A village that shelters armed men does not become a target; the armed men may, while they meet the test, and nothing else does. The discipline of pausing to identify before engaging, of asking "what exactly here makes a contribution, and is the advantage real," is the heart of distinction, and it protects the soldier as much as the population, because a casualty caused by blurring this line is tactically wasteful, legally indefensible, and strategically ruinous.

One important qualification remains. A civilian is protected from attack unless and for such time as they take a direct part in the hostilities. A civilian who picks up a weapon and joins the fighting loses their protection for as long as that direct part lasts, and may be engaged like a combatant; the moment they cease, the protection returns. This is a narrow exception, not a licence: it covers the person actually fighting, not those who merely sympathise with or support the enemy, and in doubt the presumption of civilian status holds.

Read those words exactly, because each is a limit. Direct part: the act must itself be part of the fighting and cause harm, firing a weapon, laying a mine, directing fire onto a position, not the general support of cooking, farming, or political sympathy that civilians on every side give. For such time: the loss of protection lasts only as long as the act, not the days before or after; a person who fought yesterday and is unarmed today is, again, a civilian. And the presumption of civilian status fills every gap: where you cannot tell whether what you see is a direct part in the fighting, you treat the person as the civilian the law presumes them to be. This narrow door is easy to push too wide under fear or anger, which is exactly why its edges must be known before the moment comes.

An example. A section comes under fire from a sniper in the upper window of a block of flats. The sniper is a lawful target and may be engaged. The families in the other flats are civilians and may not. Distinction is the discipline that fixes the soldier's fire on the one window and not on the building.

Proportionality

Distinction tells a soldier what may be attacked. Proportionality limits the attack even when the target is lawful. It exists because attacks on lawful military objectives sometimes cannot avoid harming civilians nearby, and the law does not pretend otherwise. What it forbids is harm out of all proportion to what the attack achieves.

The rule is this: an attack on a lawful target is forbidden if the expected incidental harm to civilians and civilian objects would be excessive in relation to the concrete and direct military advantage anticipated. A soldier must weigh, before striking, the likely harm to civilians and their property against the real and definite military gain. If the harm would be excessive against the gain, the attack must not be made, even though the target itself is lawful. The advantage weighed must be concrete and direct, a real military result, not a vague or hoped-for one, and the harm weighed is the harm that can reasonably be expected, not only what is certain.

Be exact about what sits on each side of the scale, because the two are not measured in the same coin and that is the whole difficulty. On one side is the expected incidental harm: civilians likely to be killed or injured, and civilian objects likely to be damaged, as a side effect of the attack, so far as that can reasonably be foreseen. On the other is the concrete and direct military advantage anticipated: the real, definite military result the attack is expected to produce, the firing position silenced, the crossing denied. The advantage that counts is the military one; it does not include political point-scoring, revenge, or a vague sense that destruction is generally useful. And the harm that counts is harm to civilians and civilian objects; harm to the enemy's fighters and their equipment does not weigh against the attack at all, because they are the lawful object of it.

A worked weighing makes the judgement concrete. Suppose the lawful target is a single enemy machine-gun crew of three, firing from the corner of a building, and the section commander has three feasible options for dealing with it:

   THE MACHINE-GUN CREW: weighing three options

   What is lawful:  the crew of 3, actively firing  -> a lawful target (distinction).
   The question:    what incidental harm comes with each way of attacking it,
                    and is that harm EXCESSIVE for the advantage (silencing one crew)?

   Option       Likely civilian harm            Military advantage     Verdict
   -----------  ------------------------------  --------------------  -------------------
   Precise      ~none; fire falls on the crew   crew silenced         Permitted. Best.
   small-arms   corner only
   shot

   Mortar on    a few civilians nearby may be   crew silenced         Permitted only if
   the corner   hurt; some damage to the        (same advantage)      that harm is not
                building                                              excessive, AND
                                                                      only if no less
                                                                      harmful option is
                                                                      feasible (see
                                                                      precautions).

   Air strike   many civilians in the building  crew silenced         FORBIDDEN. The
   on the whole likely killed; the building     (same advantage)      harm is excessive
   building     destroyed                                             for the advantage.

Three things stand out. First, the military advantage is the same in every row, one machine-gun crew silenced; so the rows differ only in the harm, and proportionality turns on the harm. Second, the lawful target does not justify the worst option: reaching the crew through the destruction of the building and its civilians is exactly the disproportionate attack the rule forbids. Third, proportionality and precautions run together: once a precise shot is feasible and would do the job, the heavier options are not merely weighed and allowed, they are ruled out, because the duty of precautions requires choosing the least harmful feasible means. The scale is not a licence to pick any option whose harm is "not excessive"; it works alongside the duty to keep harm as low as feasible.

This is a judgement, not a calculation, and the law asks for an honest and reasonable one made on the information available, not for perfection. But it is a real and binding limit. A lawful target does not become a blank cheque for whatever destruction reaching it would cause. A useful test for the soldier or commander: could a reasonably trained person of equivalent responsibility, knowing only what you knew at the time, justify this attack and the harm it was expected to cause? If the honest answer is no, the attack is disproportionate and must not be made.

An example. The same sniper now fires from a window in a crowded market. Calling in an air strike on the building would likely kill many civilians to remove one fighter. That incidental harm would be excessive against the advantage of killing a single sniper, so the strike is forbidden; the soldier must find another way, a precise shot, a manoeuvre, a withdrawal. Proportionality is what rules the air strike out.

Precautions

Proportionality limits what harm may be accepted; precautions require a soldier to keep that harm as low as possible in the first place. This principle is a constant duty of care, owed before and during every attack: take all feasible precautions to spare the civilian population, civilians, and civilian objects.

In practice this means doing everything feasible to verify that the target is a lawful military objective and not a protected person or place; choosing, among the means and methods available, those least likely to harm civilians; choosing the timing and approach that put civilians at least risk, striking when fewer are present rather than more; and giving effective advance warning of an attack that may affect civilians, where circumstances permit and the warning does not defeat the operation. "Feasible" means what is practicable given the situation, the information, and the risk to the force; the law does not demand the impossible, but it does demand genuine and constant care rather than indifference.

Name the four choices where precautions bite, because "take care" is too vague to act on and the law is not. Target: verify, by observation and every feasible means, that what you are about to engage is truly a lawful military objective and not a protected person or place; where doubt remains, the presumption of civilian status holds and you do not engage. Means: among the weapons and methods open to you, choose the one least likely to harm civilians that will still achieve the aim, the aimed shot rather than the area weapon, the manoeuvre rather than the strike. Timing and approach: choose the moment and route that put civilians at least risk, the hour when the market is empty rather than full, the angle whose backstop is open ground rather than a home. Warning: where circumstances permit, and where it will not defeat the operation by giving the enemy the chance to escape or prepare, give effective advance warning to the civilians who may be affected, so that they can get clear. These are not separate from distinction and proportionality; they are how a soldier honours both in the seconds before acting, by actively reducing the harm rather than merely accepting it.

There is a second face to this principle, easy to forget because it points the other way. The duties so far are precautions in attack, the care a soldier takes to spare the enemy's civilians. There is also a duty of precautions against the effects of attacks, the care a force takes to protect the civilians on its own side and under its own control: not to place military objectives in the middle of a populated area, not to fight from among civilians in a way that draws fire onto them, and to move civilians and what they depend on away from likely targets where feasible. A soldier who sites a position in a school yard, or fights from the heart of an inhabited street when open ground was at hand, has failed this duty and endangered the very people the law protects. For a home-defence force operating among its own population, this face of precautions is not a distant battlefield rule; it is the daily discipline of where you place yourself so that, if fighting comes, the people around you are shielded by your choices rather than exposed by them.

An example. Before clearing a building believed to hold enemy fighters, a commander has it observed to confirm who is inside, chooses to enter and clear it rather than destroy it from a distance, and where possible gives the occupants a chance to come out. Each is a feasible precaution taken to spare any civilians within. Precautions are the care taken before the trigger, not the regret felt after it.

Humanity, and the prohibition of unnecessary suffering

The fourth principle reaches past the protection of civilians to the conduct of the fighting itself, and to how an enemy is treated. Humanity forbids causing suffering and destruction beyond what the military aim requires. It has two faces a soldier must know.

The first is the prohibition of unnecessary suffering, sometimes called superfluous injury. The lawful purpose of force is to disable the enemy's fighters, not to make their suffering worse than that purpose needs. So the law forbids weapons and methods designed or bound to cause suffering out of all proportion to any military advantage, those that maim and torment without bringing the enemy's defeat any nearer. Particular weapons are banned for exactly this reason, and the weapons material sets them out; the principle behind every such ban is this one.

State the test behind that prohibition plainly, because it explains every weapon ban a soldier will meet. Lawful force aims to put a combatant out of the fight: to make them unable to go on fighting, whether by wounding, capture, or surrender. A weapon or method crosses the line when it adds suffering or injury that does nothing to achieve that, suffering beyond the point of putting the enemy out of the fight. The injury that incapacitates is the lawful purpose; the further torment is gratuitous, whether it comes from the design of a weapon or from a soldier's own alteration of an ordinary one. This is also why certain acts are forbidden that have no military purpose at all: an act that brings the enemy's defeat no nearer, that serves only to destroy, terrorise, or punish, fails the test at the first step, because there is no military advantage against which any harm could even be weighed. Humanity rules out both the needless way of doing a lawful thing and the doing of a thing that was never lawful to begin with.

The second face is the duty of humane treatment. Everyone who has fallen into a soldier's power, the wounded, the surrendered, the captured, the civilian under control, must be treated humanely in all circumstances, whatever side they were on. Murder, torture, cruel or degrading treatment, and humiliation are forbidden absolutely, with no exception and no excuse of necessity. This duty owes nothing to what the enemy has done; it is owed because of what the person now is, someone in your power and no longer a threat. It is the Army's value of respect for others, owed to the enemy, the wounded, the dead, and the captured, written into the law.

Mark the word absolutely, because it sets these prohibitions apart from everything else in this lesson. Distinction, proportionality, and precautions all involve judgement against necessity; humane treatment does not. There is no military advantage that can be weighed against torturing a prisoner, because the law forbids it outright, in every circumstance, with no balancing permitted. Necessity, which justifies so much, is simply not a key that opens this door. A soldier under the worst pressure, who has taken casualties and is bitter and afraid, is bound by this rule exactly as fully as one who is calm and safe, because the rule attaches not to the soldier's feelings but to the helpless state of the person in their hands. This is the point at which the law is hardest and at which keeping it matters most, and it is taught in full in Lesson 06.

An example. An enemy soldier is taken prisoner. Humanity forbids harming, humiliating, or mistreating them, regardless of what their side may have done, and requires that they be cared for and protected. The same principle forbids a weapon altered to wound more cruelly than it must. Humanity is the line, drawn through both the choice of weapon and the treatment of a captive, that necessity may never cross.

Holding the four together

The four principles work as one. Distinction chooses the target; proportionality weighs the cost; precautions reduce that cost in advance; humanity governs the means used and the treatment of those who fall into a soldier's hands. Each brings military necessity, the lawful need to win, to a halt at the point where it would become needless harm. A soldier who carries these four does not have to recall a rule for every situation. They have a settled way of seeing every situation, which is what the law of armed conflict is for.

Because the first three answer a single live question, "may I engage this, and how," they can be carried as one short sequence, run in order. The order matters: distinction comes first because if the target is not lawful, nothing later can make the attack lawful; proportionality comes next because a lawful target may still not be worth the harm; precautions come last because they shape how a permitted attack is actually carried out. Run the sequence as a decision aid:

   "MAY I ENGAGE?"   Run the gates in order. A NO at any gate stops you.

   GATE 1  DISTINCTION
           Is the target a combatant, a civilian taking a direct part now,
           or a lawful military objective (both halves of the test)?
              NO or in doubt -> presume civilian. DO NOT ENGAGE.
              YES -> go on.

   GATE 2  PROPORTIONALITY
           Is the expected incidental harm to civilians and civilian objects
           EXCESSIVE against the concrete and direct military advantage?
              YES (excessive) -> DO NOT ENGAGE. Find another way.
              NO -> go on.

   GATE 3  PRECAUTIONS
           Have I taken all feasible care -- verified the target, chosen the
           least harmful means, timed it well, warned where I can?
              NOT YET -> take them first, or choose a less harmful option.
              YES -> engagement may proceed, under the standing rules.

   (HUMANITY governs throughout: no cruel means, and humane treatment of
    anyone wounded, surrendered, or captured the moment the firing is done.)

For the Royal Kaharagian Army this sequence is something you will hold more often than you fire it, and that is the point worth ending on. The full law of armed conflict, with its targets and attacks, governs only in armed conflict, and the RKA is far likelier to be found on a relief task, a peace-support deployment, or in aid to the civil authority at home than in high-intensity war. On home soil and on humanitarian tasks there are no combatants to target; there are only people, every one of them protected, and force may be used against a person only when it is necessary to meet a threat and only as far as that threat requires. There, these principles live not through deliberate attack but through the Army's Rules for the Use of Force, which carry the same spirit into far stricter, more protective rules: distinction in the care taken to direct force only at a genuine threat, proportionality in the demand that force never exceed it, precautions in the warnings and graduated steps that come first, and humanity in the protection owed the moment a person stops resisting. Lesson 05 takes up the conduct of operations, and Lesson 08 grounds the whole course in these home and humanitarian tasks. The four principles are the understanding; the Rules for the Use of Force are how the RKA, day to day, actually keeps them.

In Practice: The Mortar by the Farmhouse

A patrol observes an enemy mortar team firing from the yard of an occupied farmhouse. Watch the four principles work in turn. The mortar crew, actively fighting, are a lawful target, while the farmhouse and the family inside it are not; the crew is what may be engaged, and nothing else. That is distinction. Calling artillery down on the whole compound would likely kill the family to remove the crew, a harm excessive against the advantage gained, so that option is ruled out. That is proportionality. Instead the commander has the position watched to confirm who is there, chooses a precise engagement of the crew alone, and waits for the moment of least risk to the civilians. Those are precautions. And when the action is over, the wounded of both sides, the enemy crew included, are searched for, collected, and cared for by need alone. That is humanity. One scene, four principles, and a lawful result that no single rule could have reached on its own.

Now run the same scene through the decision aid, gate by gate, to see how the sequence forces the lawful answer. At Gate 1, distinction, the crew firing the mortar make a contribution to the enemy's military action by their very use, and silencing them offers a definite advantage; both halves of the test hold, so they are a lawful target, while the farmhouse and the family plainly are not. At Gate 2, proportionality, the heavy option, artillery on the compound, fails at once: the expected death of the family is excessive against the advantage of silencing one crew, so that option is barred, and only an engagement whose expected harm to the family is not excessive may go forward. At Gate 3, precautions, the commander does not simply take the first option that passes the gate; he takes the feasible steps that make the harm smaller still, observing to confirm exactly who is in the yard, choosing the precise engagement of the crew rather than any area weapon, and waiting for the moment the civilians are at least risk. Only then does the engagement proceed. And humanity governs the whole of it and outlasts it: no cruel means is used against the crew, and when the firing stops, the wounded of both sides are collected and cared for by need alone, the enemy included, because they are now people in the patrol's power and no longer a threat. The result the patrol reaches, the crew dealt with and the family unharmed, is not luck. It is what running the four principles in order produces, and what skipping any one of them would have lost.

Check Your Understanding

State the four principles, and explain how each one is different from the others. Which principle do the other three rest upon, and why?
Distinction makes a target lawful; proportionality may still forbid the attack. Using the sniper examples, explain how both can be true of the same target in different surroundings. Then take the machine-gun crew: explain why the air strike on the whole building is forbidden when a precise shot is available, naming both the principle that weighs the harm and the principle that rules out the heavier option.
Explain what military necessity permits and what it never permits. Give an example of an action that necessity might seem to favour but that humanity forbids, and explain why no claim of necessity can make that action lawful.

Reflection (write a short paragraph): Of the four principles, which do you think would be hardest to hold to under fear, anger, or fatigue, and why? Think of how that principle might be tested in a real moment, and what habit or understanding, settled now, would help you keep it when it is hard.

Summary

The four principles are the working core of the law: distinction, proportionality, precautions, and humanity. They strike the balance between military necessity and humanity in practice. Necessity permits lawful force but never licenses cruelty. The first three answer one live question, "may I engage, and how," and are best carried as an ordered sequence: distinction, then proportionality, then precautions.
Distinction: attack only combatants and military objectives, never civilians or civilian objects; in doubt, presume civilian. An object is a military objective only when both halves hold, an effective contribution by nature, location, purpose, or use, and a definite military advantage from its destruction or capture. A civilian who takes a direct part in hostilities loses protection only for as long as that lasts.
Proportionality: even against a lawful target, an attack is forbidden if the expected incidental harm to civilians would be excessive against the concrete and direct military advantage anticipated. Weigh civilian harm on one side against real military advantage on the other; harm to the enemy's fighters does not weigh against the attack. A lawful target is never a blank cheque.
Precautions: a constant duty to take all feasible care to spare civilians, in the choice of target, means, and timing, and to warn where circumstances permit, choosing the least harmful feasible option. There is also a duty of precautions against the effects of attacks, to shield the civilians on one's own side by where one places oneself and one's positions.
Humanity: forbids weapons and methods causing unnecessary suffering, and acts with no military purpose, and requires humane treatment of all who fall into a soldier's power, whatever side they were on. Humane treatment is absolute: no necessity, pressure, or provocation can excuse mistreating someone in your hands. It is the Army's value of respect for others written into the law.
For the RKA, these principles live most often not through attack but through the Rules for the Use of Force on home-soil and relief tasks, where there are no combatants to target, only people to protect, and force is used only when necessary and only as far as a threat requires. Lesson 04 sets out who and what is protected, Lesson 05 the conduct of operations, and Lesson 08 the home and humanitarian tasks the Army most often undertakes.

The Four Principles