WASHINGTON — One hundred years after a spark in Central Europe ignited a conflagration from which the world has not yet recovered and from which Europe will never recover, armed forces have crossed an international border in Central Europe, eliciting this analysis from Secretary of State John Kerry: “It’s a 19th century act in the 21st century. It really puts at question Russia’s capacity to be within the G8.”

Although this “19th century act” resembles many 20th century (and 16th, 17th and 18th century) acts, it is, the flabbergasted Kerry thinks, astonishing in the 21st century, which he evidently supposes to be entirely unlike any other. What is more disconcerting — that Kerry believes this? Or that his response to Vladimir Putin’s aggression is to question Russia’s “capacity” — Kerry means fitness — for membership in the G8?

For many centuries, European peace has been regularly broken because national borders do not tidily coincide with ethnic, linguistic and religious patterns. This problem was intensified by World War I, which demolished the Habsburg, Romanov and Ottoman empires. Ukraine is a shard of the first two, and a neighbor of a remnant of the third.

The problems bequeathed by that war were aggravated by a peacemaker, one of Kerry’s precursors among American progressives eager to share with the world their expertise at imposing rationality on untidy societies. Unfortunately, Woodrow Wilson’s earnestness about improving the world was larger than his appreciation of how the world’s complexities can cause improvers to make matters worse.

Wilson injected into diplomatic discourse the idea that “self-determination” is a universal right and “an imperative principle of action.” Several of his Fourteen Points concerned self-determination. But of what “self” was he speaking? Sometimes he spoke of the self-determination of “nations,” at other times of “peoples,” as though these are synonyms. Wilson’s secretary of state, Robert Lansing, wondered “what unit has he in mind” and warned that “certain phrases” of Wilson’s “have not been thought out.” But they resonated. In the Atlantic Charter of 1941, Franklin Roosevelt and Winston Churchill affirmed the rights of “peoples.” The U.N. Charter endorses the self-determination of “peoples.” Which became a third ingredient, ethnic self-determination. Wilson had sown dragon’s teeth.

Lansing said the “undigested” word “self-determination” is “loaded with dynamite. ... It will, I fear, cost thousands of lives.” While Wilson was making phrases in 1918, a German corporal recovering from a gas attack was making plans. And on Sept. 27, 1938, the corporal, then Germany’s chancellor, said “the right of self-determination, which had been proclaimed by President Wilson as the most important basis of national life, was simply denied to the Sudeten Germans” and must be enforced. So Czechoslovakia was dismembered. Still, the war came.

Three months from the end of the war in Europe, the architects of the impending victory — Roosevelt, Churchill and Stalin — met at a town on the Crimean peninsula where Putin is now tightening his grip. Conservatives who should know better have often said the Yalta Conference “gave” Eastern Europe to the Soviet Union. Actually, the Red Army was in the process of acquiring it. This process could no more have been resisted militarily by Stalin’s allies, which the United States and Britain then were, than Putin’s aggression can be.

“You may not be interested in war, but war is interested in you,” supposedly said Lev Bronstein, as Leon Trotsky was known when he lived in the Bronx, before he made the Red Army, the parent of the forces Putin is wielding. Barack Obama, who involved the United States in seven months of war with Libya, perhaps because the project was untainted by U.S. national interest, is seeking diplomatic and especially economic leverage against Putin’s ramshackle nation in order to advance the enormous U.S. interest in depriving him of Ukraine.

Unless Obama finds such leverage, his precipitous slide into Jimmy Carter territory will continue. As an expression of disdain for a U.S. president, Putin’s seizure of Ukraine’s Crimean peninsula is symmetrical with Leonid Brezhnev’s invasion of Afghanistan late in Carter’s presidency. Large presidential failures cannot be hermetically sealed; they permeate a presidency. Putin’s contribution to the miniaturization of Obama comes in the context of Obama’s self-inflicted wound — Obamacare, which simultaneously shattered belief in his competence and honesty, and may linger as ruinously for Obama as the Iranian hostage crisis did for Carter.

This may be condign punishment for Obama’s foreign policy carelessness and for his wishful thinking about Putin as a “partner” and about a fiction (“the international community”) being consequential. It certainly is dangerous.

George Will is a columnist with the Washington Post Writers Group.