Mikheil Saakashvili was president of Georgia from 2004 to 2013. He is a senior statesman at Tufts University’s Fletcher School of Law and Diplomacy.

In July 2008, the government of Georgia was under considerable pressure: Russia was organizing provocations in two regions of our country and amassing troops at our border. Almost every Western politician to whom my government raised concerns in those days said that Russia would not attack and urged us to keep calm and not react to Russian moves. My friend Otto von Habsburg, one of Europe’s most experienced politicians, was less reassuring. He bluntly predicted that Russia would attack with all the military might at its disposal, no matter what Georgia did to avoid such an outcome. History repeats itself, he told me.

A few weeks later, tens of thousands of Russian soldiers crossed our border, and planes started bombing us round the clock. While Vladi­mir Putin failed to achieve his ultimate goal, to take over Georgia’s capital, his troops still occupy a fifth of my country’s territory.

There are striking similarities between the early stages of Russian aggression against Georgia and what is happening in Ukraine. Watching recent events and the global response, I keep thinking about history repeating itself — and other instances of aggression in Europe.

In the 1930s, Nazi Germany occupied part of neighboring Czechoslovakia under the pretext of protecting ethnic Germans. Today, Russia is claiming to protect ethnic Russians — or people with hastily distributed Russian passports — in Crimea or Georgian territories. In September 1938, when Germany annexed the Sudetenland, British Prime Minister Neville Chamberlain called the situation “a quarrel in a far-away country, between people of whom we know nothing.” Similarly, some today question whether the West should bother about Ukraine, saying Russia has more at stake than the West. Many in the West are talking about the need to reach some kind of compromise with Russia, an option that smacks of Munich 80 years ago. They claim to be motivated by such common strategic interests as nonproliferation and the fight against terrorism; by the same token, under the guise of needing to contain the Soviet Union and stop the spread of communism, Chamberlain reached a deal with Hitler. Now, of course, we know that all attempts to appease the Nazis led the big European powers to feed one country after another to Hitler and, ultimately, led to World War II.

Such global catastrophes are what happens when the established international order collapses and rules no longer apply. Ukraine is just the most vivid recent demonstration. Imagine if Ukraine hadn’t given up its considerable nuclear arsenal in the 1990s. To persuade the Ukrainians to do so, the United States and Britain, together with Russia, signed agreements guaranteeing Ukraine’s territorial integrity in exchange for Ukraine giving its weapons to Russia. And yet, here we are.

But then, the European Union and Russia signed an agreement providing for the withdrawal of Russian forces from Georgia in 2008. Russia never complied — something our European guarantors seldom mention.

Putin’s motivations are similar to those of prewar Germany: He wants to rectify what he sees as unjust treatment and humiliation by Western powers after the Cold War. He is trying to reconquer lost lands and grab natural resources. Little has been said about the offshore oil resources in Abkhazia that the Russian state monopoly Rosneft confiscated in 2009. U.S. companies have invested considerably in shale gas fields off Crimea. But Ukraine’s emergence as self-sufficient in energy, and even a major gas exporter to Europe, would be Putin’s ultimate nightmare.

Putin destabilizes his neighbors in an effort to kill any NATO and E.U. appetite for further expansion. He also sees periodic land grabs as, somehow, the route to his domestic political rejuvenation. There is a logic to his perception of ideological threats: If Ukraine ceased to be a corrupt oligarchy and became a real European democracy, Putin’s opponents would see the contrast — and potential benefit to fighting their own reality.

Why should the West care about what happens in Ukraine? We are seeing not just the slicing up of Europe’s largest country but also the destruction of post-Cold War order in Europe. This order was based on clear rules that not only protect small countries but also ensure stability and prosperity for the bigger ones, protect minorities and settle conflicts by peaceful mechanisms. Think of the ramifications if borders across the continent were to revert to ethnic lines. If there are no longer any rules, a spiraling cycle of violence and destruction is inevitable.

Such an outcome could still be avoided. The U.S. sanctions announced Thursday are a good first step. They should be implemented immediately, and Europe needs to strengthen its own response. Ukraine, Georgia and Moldova should be put on fast-track accession to the European Union and granted membership action plans for NATO to demonstrate that Russia cannot seize its ends through illegal means.

We don’t need another visionary like Churchill to know what to do next. Today’s democracies have enough experience; applied with common sense and a modicum of courage, we can avoid the worst.