But after dismembering Poland, and dividing its spoils with the Soviet Union, Hitler unexpectedly absorbed Denmark and Norway the next spring. Then in May 1940, he successfully invaded Belgium, France, Holland, and Luxembourg. He tried to bomb Britain into submission. The conflict eventually spread to the Mediterranean and became truly a “world war” in 1941 with the surprise Axis attacks on the Soviet Union and the Japanese bombing of Pearl Harbor.

Sixty million people would perish in the six years of war, more than any man-caused or natural calamity in history—and World War II would become one of the few conflicts in history in which the losers suffered far fewer fatalities than did the winners. Yet the lessons of World War II endure and had, until recently, guided our foreign policy successfully.

The war taught us that deterrence matters, far more than multiparty arms-limitation treaties, world bodies like the League of Nations, or guarantees from dictators at widely publicized summits. Hitler’s Nazi military in 1939 was weaker and smaller than the combined might of the Western European democracies. Its planes and tanks were no better and in many cases clearly inferior to French armor and British fighters and bombers. Yet Hitler guessed rightly that after six years of appeasing Germany, the democracies were in no mood for war in 1939-40. He was again proven right when France, which had helped to defeat Germany in World War I, collapsed in just six weeks.

Deterrence, however, is not just calibrated by soldiers and weapons. The mettle of leaders counts just as much. Today, the military of Vladimir Putin’s Russia is hardly omnipotent. But Putin’s unpredictable aggression is predicated on his belief that the more powerful democracies will not want to deal with the hassles and costs of stopping him.

But such concessions to dictatorships only strengthen them while undermining internal dissenters. Generals of the German general staff, conservative Prussian aristocrats, and liberal reformers were all terrified of Hitler by 1939. As early as 1936, some had even sought to remove Hitler and his gang through half-baked plots. But each time the Allies backed off during an international crisis—and as Hitler added Austrian, Czech, and Polish territories to the growing Third Reich—his popularity with everyday Germans soared—and designs to remove him fizzled. After the war, early opponents of Nazism confessed that French and British appeasement had empowered Hitler and undermined their efforts.

Perceived momentum counts. The majority of the public and nations at large have no real ideology other than a wish to ally themselves with a winner. After the fall of France in June 1940, Germans mobbed the streets to catch a glimpse of their Fuhrer; yet after the Wehrmacht’s catastrophe at Stalingrad in early 1943, Hitler was afraid to speak to everyday Germans and went into virtual seclusion. Indeed, when the war went badly in mid-1944, his own military once again tried to blow him up.

Likewise, most of Eastern Europe had been awed by the Third Reich after its unprecedented victories in the West. Within a year, almost all of these nations deemed Hitler unstoppable and logically chose to join his Axis alliance—Hungary and Romania in November 1940, Bulgaria in March 1941, and Yugoslavia one month later. But by early 1945, as the Red Army in the east and Allied ground forces in the West neared the borders of a collapsing Nazi Germany, those same nations began abandoning Hitler, the assumed loser.

A similar dynamic is at work today with Islamic terrorists. Organizations like ISIS and al Qaeda gain recruits and win stealthily with help from Islamist nations when they pull off successful and brutal attacks against soft Western targets. Empty redlines empower the patrons of these weak bullies. In contrast, terrorists and their supporters lose credibility when they are humiliated, bombed, or see their leaders captured or killed. Bashar Assad, tottering on the brink of defeat and internal defection, recalibrated his control over Syria once the U.S. backed off from its prior threat to bomb him if he used chemical weapons.

We sometimes hope that reaching out to the Taliban or radical Islamists will lessen tensions. But usually such magnanimity is seen as weakness, unless the war has been clearly going our way. Hitler admired the strength of Stalin who eventually crushed him, and loathed the Allied governments that had once conceded to his every wish.

By the same token, current agreements with dictators in Cuba or Iran should have had none of the urgency of the détente of the 1970s with a USSR armed to the teeth with nuclear missiles pointed at the U.S. Such optional foreign policy accords with our twenty-first-century enemies may superficially appear to calm tensions, but in truth such outreach more likely sabotages Iranian and Cuban dissidents, while ensuring unearned popularity for Iran’s theocratic Ayatollahs and Cuba’s Castro Brothers, who all brag on their censored media how the U.S. gave into their demands.

Geography and national character are likewise unchanging. Hitler learned the lesson of Napoleon that it is suicidal to invade Russia from the West. The distances are too long, the campaign season is too short, and Russians fight quite differently on their homeland than abroad. The Red Army, unstoppable inside Russia, lagged in 1939 during its invasions of Poland and Finland, and slowed when it advanced into Eastern Europe in 1945. The best way to deter Putin is probably not to send ground troops inside the former Soviet Union.

Japan and China, whose disputes of the 1930s helped to trigger the Pacific war, will always likely remain in some sort of conflict. The proximity of the two antithetical civilizations—the one, a land power with a huge population and territory, the other, an island naval power with a highly capable, disciplined, and cohesive population—ensures that age-old tensions will transcend the particular political disputes of the moment. Likewise, Eastern Europe will always look for support from Western Europe and the United States—and often in vain. Its unfortunate geography puts these vulnerable countries in the bind of being squeezed between a vast Russia and the economic and cultural powerhouse of Germany. No wonder that our best U.S. foreign policy experts were schooled in World War II and learned that keeping the peace between both Germany and Russia, and China and Japan, should be the cornerstones of American alliance-building and diplomacy.

In the postmodern age, we scoff at the Cold War anachronism of NATO. But its 1949 informal mission statement was not just to deter a communist Soviet Union from invading democratic Western Europe. In truth, according to the words of General Hastings Ismay, the first secretary general of NATO, the alliance aimed “to keep the Russians out, the Americans in, and the Germans down.”

That formula endures and is yet another valuable lesson from World War II. Germany, currently the banker of Europe and arbiter of European immigration policy, is a force for good—when integrated within NATO and the European Union, and as a non-nuclear partner with nuclear Britain and France. Russia is Russia, whether communist or not, and causes trouble when it looks westward into Europe. And the United States must always fight its natural isolationist proclivities to stay engaged abroad and to put out small fires before they become global conflagrations.

The ending of World War II is also instructive. The settlement of 1945 followed the destruction and occupation of German, Italy, and Japan. All these Axis countries were monitored by peacekeeping troops of the victors, which, incidentally, still have bases inside the borders of their former enemies. Their constitutions were rewritten by the Allies; their militaries were disarmed; and they were made allies of the winners.

We sometimes believe the far milder Versailles Treaty of 1919 that formally ended World War I caused World War II. It probably did, but certainly not in the way that most think: Versailles was not too harsh, but rather combined the worst of both worlds in superficially humiliating Germany without concrete efforts to occupy its ground and monitor its postwar recovery. The Allies did not repeat that mistake in 1945 and the world has so far earned a peace of sorts for seventy, rather than a mere twenty, years.

The tragedy of World War II was that 60 million people perished to confirm that the United States, the Soviet Union, and Great Britain were far stronger than the fascist powers of Germany, Japan, and Italy—a fact that should have been self-evident in 1941 and in no need of such a bloody proof, if not for prior British appeasement, American isolationism, and Russian collaboration.

Original article here.