“JAPAN SURRENDERS, END OF WAR!” So screamed the front page of the normally sedate New York Times on Aug. 15, 1945 — 75 years ago this Saturday. When the news had flashed on the moving electric sign in Times Square the night before, the newspaper reported, half a million revelers let out a “victory roar” that “beat upon the eardrums until it numbed the senses. For twenty minutes wave after wave of that joyous roar surged forth.”

The elation on V-J Day was understandable. World War II had been the costliest conflict in history, claiming some 60 million lives, 418,500 Americans among them. But the war’s end simply marked a new phase of the struggle to establish a peaceful world order. While Allied leaders were far more successful in peacemaking than they had been after World War I, their failures were costly and haunt us to this day.

It is worth remembering what the United States got right and wrong after 1945, because today we labor under a uniquely ignorant president who thinks that the 1918 influenza broke out in 1917 and that it “probably ended the Second World War.” Not knowing much about history (or anything else, other than self-promotion), President Trump seems eager to fritter away the best decisions of the Greatest Generation while repeating its worst mistakes.

We tend to remember what the United States got right after 1945 — and there was a great deal of it. Enlightened American proconsuls — Gen. Douglas MacArthur in Japan and Gen. Lucius D. Clay in Germany — helped to transform illiberal enemies into democratic friends. The United States helped midwife a series of international institutions — the United Nations, NATO, the World Bank, the International Monetary Fund, the General Agreement on Tariffs and Trade (GATT) — to shape a more liberal world order. All of these organizations were flawed, but they would prove far more durable than post-World War I creations such as the League of Nations and the Kellogg-Briand Pact.

Their success owed a great deal to the willingness of the Greatest Generation to ignore the siren song of isolationism. The United States was generous with reconstruction aid (the Marshall Plan alone distributed $13 billion, or $135 billion in today’s money), and, instead of bringing the “boys” home, we kept hundreds of thousands of troops in Asia and Europe.

Those were farsighted decisions, but the postwar order was also deeply flawed. The Red Army occupied Eastern Europe, turning the region into a Soviet satrapy for more than four decades. Joseph Stalin’s troops also advanced into Manchuria, China’s industrial heartland, helping speed Mao Zedong’s victory in China’s civil war.

Soviet troops likewise marched into northern Korea while U.S. forces landed in the south to oversee the surrender of Japanese forces. Thus was born the division of the Korean Peninsula that persists to the present day — with North Korea now a nuclear threat. The division of Indochina took longer — it would not occur until 1954 — but it was a foregone conclusion that communists would rule at least part of Vietnam after they took over neighboring China in 1949 and began providing weapons and advisers to Ho Chi Minh in his struggle against the French.

In both cases the United States was dragged into costly conflicts in geopolitical backwaters whose fates had been of scant concern to policymakers during World War II. The decision to divide Korea at the 38th parallel was hastily made by two U.S. Army colonels studying a National Geographic map at the Pentagon on the evening of Aug. 10, 1945. Those zones of occupation had hardened into separate states by 1948. The North invaded the South two years later, after Secretary of State Dean Acheson notoriously excluded South Korea from the United States’ “defensive perimeter” in Asia. Meanwhile, in Vietnam, growing U.S. support for the French war effort against the Vietminh dragged us into our own brushfire war. The U.S. wars in Korea and Vietnam — an unforeseen and unwelcome byproduct of World War II — would claim the lives of nearly 100,000 Americans.

It could have been much worse; at least we avoided having the Cold War turn into a nuclear war. But the post-1945 experience confirms what Foreign Affairs editor Gideon Rose wrote in “How Wars End: Why We Always Fight the Last Battle”: “Ending a war successfully involves establishing durable political arrangements for the territories in question ... [but] American leaders have repeatedly botched this challenge by making a variety of unforced errors.”

Our unforced errors continue to this day. Trump appears determined to withdraw the remaining U.S. forces from Afghanistan, even though no political concord with the Taliban has been forged. He is launching a new “cold war” with China and ramping up hostilities with Iran, with no end in sight. And he is heedlessly sabotaging the post-1945 world order by pulling a third of the U.S. troops out of Germany, belittling U.S. allies, and undermining institutions such as NATO and the World Trade Organization (successor to GATT). He even repeats the “America First” slogan used by isolationists of the 1930s.

Some people never learn.

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