For conquest
Wars of conquest are unjust and he is chargeable with all the evils, all the horrors of the war: all the effusion of blood, the desolation of families, the guilt of rapine, the acts of violence, the ravages, the conflagrations, are his works and his crimes. He is guilty of a crime against the enemy, whom he attacks, oppresses, and massacres without cause: he is guilty of a crime against his people, whom he forces into acts of injustice, and exposes to danger, without reason or necessity—against those of his subjects who are ruined or distressed by the war—who lose their lives, their property, or their health, in consequence of it: finally, he is guilty of a crime against mankind in general, whose peace he disturbs, and to whom he sets a pernicious example.
—Emerich de Vattel. The Law of Nations, 1758.
It is not a war of conquest when the people being invaded have no freedom, when the purpose is to give it to them and/or to punish them for their attacks on others.
For dignity
They tell you, Sir, that your dignity is tied to it. I know not how it happens, but this dignity of yours is a terrible encumbrance to you; for it has of late been ever at war with your interest, your equity, and every idea of your policy. Show the thing you contend for to be reason; show it to be common sense; show it to be the means of attaining some useful end; and then I am content to allow it what dignity you please. But what dignity is derived from the perseverance in absurdity, is more than ever I could discern.
—Edmund Burke. Speech on American Taxation, April 19, 1774.
True dignity and pride can only come from a reputation for adhering always to honor and justice—never by assailing others. True strength of character in a nation, as in a person, comes from being prepared to eat humble pie when we find ourselves in the wrong, and in ignoring slights.
Where right is debatable
Nature gives us no right to have recourse to forcible means, except where gentle and pacific methods prove ineffectual. It is not permitted to be so inflexible in uncertain and doubtful questions. Who will dare to insist that another shall immediately, and without examination, relinquish to him a disputable right? This would be a means of rendering wars perpetual and inevitable. Both the contending parties may be equally convinced of the justice of their claims: why, therefore, should either yield to the other? In such a case, they can only demand an examination of the question, propose a conference or an arbitration, or offer to settle the point by articles of agreement.
—Emerich de Vattel. The Law of Nations, 1758.
If the dispute is one which, if it were between individuals, would be dealt with by the civil courts, then recourse to violence should never be taken. Only if the dispute is one which, if it were between individuals, would be dealt with by the criminal courts, is violence acceptable. Otherwise civilization demands that the conference table is the proper way to deal with a dispute. Unlike individuals, there are only a small number of nations. A country that acquires a reputation for unfair dealing, or for ignoring arbitration, will eventually suffer the most for it. Until then, a respect for peace requires that the aggrieved nation, even if easily able to enforce its rights through force, turn the other cheek.
Believing it will be easy or short
Beware, my friends, of the first step, and know your whole journey before you move one foot; when you are up to the ears in mire, it will be too late to look back. At first we may be told by our confederates and their creatures, that we need only bounce a little, and make a show of force, and everything will go to our mind; but a burnt child will dread the fire: When we are engaged, we cannot retreat; one step will draw another; it will not depend upon ourselves, whether we shall go on or not; the game will be then in other hands, who will play it to their own advantage, without regarding ours; and what we begin in wantonness, will probably end in our confusion.
—John Trenchard. Cato’s Letters No. 86, The terrible consequences of a war to England, and reasons against engaging in one, Saturday, July 21, 1722.
Let us learn our lessons. Never, never, never believe any war will be smooth and easy, or that anyone who embarks on the strange voyage can measure the tides and hurricanes he will encounter. The statesman who yields to war fever must realize that once the signal is given, he is no longer the master of policy but the slave of unforeseeable and uncontrollable events. Antiquated war offices, weak, incompetent or arrogant commanders, untrustworthy allies, hostile neutrals, malignant fortune, ugly surprises, awful miscalculations—all take their seat at the council board on the morrow of a declaration of war.
—Winston Churchill. My Early Life, 1930.
General war is the most terrible and exhausting ordeal a nation can go through. But even wars against isolated, and militarily inferior, foes tend to drag out for decades and sap the treasuries of the wealthiest nations. Apart from punitive actions taken against a small country by an overwhelmingly superior antagonist, history supplies very few examples of short and sharp campaigns, and even these—like lottery winnings—should never be counted on.
Without the realistic ability to reach a defined goal
Hence, the intervention created its own painful choice: either the UN would make Somalia into a colony and spend decades engaged in nation-building, or the UN forces would withdraw in due course and Somalia revert to its prior anarchy … . Military intervention without an attainable purpose creates as many problems as it solves.
—Margaret Thatcher. The Path to Power, 1995.
It is relatively easy to defeat a tin-pot dictatorship, but to convert the conquered country into a liberal democracy is the hardest task imaginable. To guarantee success requires the modern equivalent of internment camps such as the British used in Malaysia. If this is to be undertaken, it must be sanctioned by referendum; the people should be asked whether they are prepared to significantly increase taxes and hold the effort for up to twenty years. If not, then the war aims should be limited to executing the tyrant and his henchmen and leaving. Attempting to fudge the process by relying on tribal elders, mullahs, and heroin-cultivating warlords to maintain peace and ultimately civilize the country is doomed to failure.
Some goals cannot be achieved, no matter how many lives or how much wealth is lavished on them. The prime example is the goal of making ethnic groups that traditionally despise each other coexist peacefully. History shows that the only practical solution is to physically separate them.
Often
Engaging in war is strategically damaging. The occasional punitive action can be undertaken with little interruption to economic growth, but protracted wars like Vietnam, Iraq, and Afghanistan lead to crippling debt and ultimately lost decades of little or no economic growth. These lost decades are not lost to those nations that stayed out of the war, and the resultant differing rates of growth lead to permanent shifts in the balance of power.
Warmongers should study the effects of the Elizabethan Golden Age on England. Elizabeth I resisted every ingenious, earnest, and undeniable argument her counsellors made for going to war. She thereby provided her country with a lengthy respite from the curse of war and set it on a course to dominate the colonization of North America and to accumulate the capital needed to launch the Industrial Revolution and so to eclipse all other nations of the world in commercial prosperity and influence.
In applying this lesson to the modern era, it is vital that the United States stays out of protracted wars. If it continues to exhaust itself with debilitating conflicts while China steadily and peacefully expands its power, it will quickly find itself eclipsed and in mortal peril.
