confronts potential predators with the prospect of pain sufficient to restrain them from breaking the peace. Even with a vast body of international conventions and a U.N. Security Council endowed with powers greater than any wielded by any previous international institution, states ultimately rely on their own ability to protect their interests and to dissuade those who would attempt to damage those interests from doing so by the threat of punishment greater than any gain that might be achieved. As noted, this principle has been far from infallible and not necessarily because those who lead states are "evil" but because state interests may clash and governments seek by one means or another to enhance theirs, if necessary at the expense of those of another state.
4. In the prenuclear age, rulers of states (and their predecessor entities) were frequently deterred from seeking to achieve gains at the expense of other states by fear of the cost. Instead, they sought their goals by negotiation, dynastic marriages, and other ways short of recourse to arms. But frequently they did have recourse to arms, especially if the other state or states were thought to be weaker. Often this involved miscalculations and the enterprise was suspended; or perhaps a deal was made. The costs incurred were frequently temporary: destruction could be repaired; populations could be replenished; debts could be paid, covered by loans, or ignored. Occasionally, of course, damage, whether as a result of gains achieved or of losses suffered or of merely a standoff, could be severe and long lasting (e.g., the Thirty Years' War and World Wars I and II). Sometimes states ceased to exist or lost their independence. Major changes in the international system could result. But over time the effects of even the more cataclysmic conflicts and resulting transformations in the state system would be absorbed and surmounted.
5. In the last 150 years or so, the prompt damage and injury inflicted by weapons of war greatly increased; cumulative damage and injury extended well beyond the military forces of warring parties; weapons could be delivered against military and civilian targets over ever-increasing distances and with ever-greater rapidity. Combined with ever-more effective means of conflict, like blockades and displacements and destruction of civilian populations, prenuclear conflicts in the 20th century came to resemble the most destructive conflicts in the Middle Ages and antiquity. Many people came to conclude in the early 20th century, especially after World War I, that modern war was not worth any conceivable gain. As it turned out, the deterrent effect of war itself was far from universal. Indeed, the destructiveness of modern prenuclear war was exploited by the most ruthless political movements and leaders between the world wars to advance their ambitions. The famous Leni Riefenstahl movie "Triumph of the Will" was designed both to imbue the German public with a sense of destiny and to intimidate the rest of Europe into meeting German demands and to persuade it that resistance would be senseless should Germany use force to impose them.