For a time, reset, concessions and appeasement work to delay wars. But finally, nations wake up, grasp their blunders, rearm and face down enemies. That gets dangerous. The shocked aggressors cannot quite believe that their targets are suddenly serious and willing to punch back. Usually, the bullies foolishly press aggression, and war breaks out. It was insane of Nazi Germany and its Axis partners to even imagine that they could defeat the Allied trio of Imperial Britain, the Soviet Union and the United States.

Hitler figured that for a decade America had been unarmed and isolationist. Britain repeatedly had appeased the Third Reich. The Soviets initially collaborated with Hitler. Hitler met no opposition after militarizing the Rhineland. He annexed Austria with impunity. He gobbled up Czechoslovakia without opposition. Why shouldn’t Hitler have been stunned in 1939 when exasperated Britain and France finally declared war over his invasion of distant Poland? Six years of war and some 60 million dead followed, re-establishing what should have been the obvious fact that democracies would not commit suicide.

By 1979, the Jimmy Carter administration had drastically cut the defense budget. President Carter promised that he would make human rights govern American foreign policy. It sounded great to Americans after Vietnam ― and even greater to America’s enemies.

Then Iran imploded. The American embassy in Tehran was stormed. Diplomats were taken hostage. Radical Islamic terrorism spread throughout the Middle East. Communist insurrection followed throughout Central America.

The Soviet Union invaded Afghanistan. China went into Vietnam. Dictators such as the Soviet Union’s Leonid Brezhnev and Iran’s Ayatollah Ruhollah Khomeini assumed that Mr. Carter no longer was willing to protect the U.S. postwar order. Or perhaps they figured that the inexperienced American president was too weak to respond even had he wished to do so.

Then, Ronald Reagan defeated Mr. Carter in 1980 on the promise of restoring U.S. power. At first, both America’s friends and enemies were aghast at Reagan’s simplistic worldview that free markets were better than communism, that democracy was superior to dictatorship, and that in the ensuing struggle, the West would win and the rest would lose.

From 1981 to 1983, Reagan was caricatured even at home as a cowboy ― not the statesman later to be known for restoring U.S. prestige and global stability, and for helping to bring down Soviet imperial communism.