WE DIDN’T NOTICE IT at the time, but the post-Cold War world changed on Oct. 1, 1999, when Russian Prime Minister Vladimir Putin used the bombing of a Moscow apartment building on Sept. 9 as a pretext to destroy the semi-independent Chechen Republic accepted by Boris Yeltsin in 1996. This and other bombings around Russia were claimed, but never proven, to be the work of Chechens.

Chechnya has been ruled by Russia since the early 19th Century. Through czars, commissars and oligarchs, warfare and mutual atrocities have been almost continuous. Mr. Putin’s clear-headed, decisive and brutal action contrasted with Boris Yeltsin’s erratic behavior, was highly popular, and elected him president in 2000. Political stability, religious freedom and an improving economy based on oil revenue have kept him popular, despite the suppression of political opposition, the murder of journalists, the destruction of competitive challengers to chosen oligarchs, and lies about the government’s deadly mishandling of occupations by Chechen terrorists of a Moscow theater, in 2002, and a school in Beslan, North Osettia, in 2004.

In the “Near Abroad” –– the 14 non-Russian former Soviet republics –– Mr. Putin has ham-handedly tried to re-establish Russian hegemony. He tried to rig the Ukrainian presidential election of 2004, and when the nearly murdered Viktor Yushchenko was elected anyway, he reneged on a contract and abruptly cut off natural gas to Ukraine and Western Europe during the coldest winter in 25 years. When Mikheil Saakashvili, an American-educated democrat, was elected president of Georgia, Russia cut off air, rail and mail, and expelled ethnic Georgians from Russian schools.

President Bush missed nearly all of this. He had “looked into Putin’s soul” and liked what he saw. Mr. Putin had only to go speedboating off Kennebunkport to assure the American Psychologist-in-Chief that all was well in hand. When Russia launched a massive invasion of Georgia, on Aug. 8, Mr. Bush was doing a photo-op with the girls’ volleyball team in Beijing. Mr. Putin was in Beijing, too, but he immediately flew to Russian-ruled North Ossetia to urge on Russian “volunteers” invading nominally Georgian-ruled South Ossetia. At that moment we saw an American president in name who was really an ex-president, and a Russian ex-president in name who is really the president.

At this writing we do not know the exact “for want of a nail the shoe was lost . . .” that started this war. The Russians say Mr. Saakashvili, put in a reckless frame of mind by American meddling, used the cover of the Olympics to invade South Ossetia, kill Russian peace-keepers and “commit genocide.” Mr. Saakashvili says that separatists controlled by Russia attacked Georgian positions. When, after offering a unilateral cease-fire, Georgia defended herself, Russia instigated a pre-planned invasion. Georgian troop movements seem to indicate days of planning. Russian troop movements and a cyber-attack seem to indicate weeks of planning.

The certain truth is that under Mr. Putin, Russia has never respected international law as it applies to the sovereignty of other former Soviet Republics. Russia sees the development of their democracy and good relations with the West as invasions of her “sphere of influence” –– while pursuing renewed influence in Cuba and Nicaragua, as is her right.

Harry Truman might have sent troops to Georgia if Russia did not remove her “volunteers.” Unfortunately, the wars in Iraq and Afghanistan have strategically tied down the United States. Worse, under President Bush and his strident political opponents, the nation has lost its unity. If the world changed on Oct. 1, 1999, many only came to understand it on Aug 8, 2008. We must hope that now includes Messrs. Bush and Obama. (John McCain has understood it for a long time.)

This is renascent Russian imperialism, and democratic nations are going to have to deal with it. If Russia takes Georgia or succeeds in deposing President Saakashvili in favor of a puppet, Moldova, where Russia has troops, may be next, with the real prize being Ukraine. Except for a few old, fat communists in Crimea, no one in Ukraine wants to be ruled by Russia. But many educated, democratic-mind Russians do not recognize Ukraine as a nation. It’s a bit like the historic British blind spot with regard to Ireland.

The leaders of five onetime captive nations showed they understand the stakes: On Aug. 12, Presidents Toomas Ilves, of Estonia, Valdas Adamkus, of Lithuania, Lech Kaczynski, of Poland, Viktor Yushchenko, of Ukraine, and Prime Minister Ivars Godmanis, of Latvia, traveled to Tbilisi, the Georgian capital, to appear alongside President Saakashvili at a huge patriotic rally. These leaders understand that the new Russian imperialism is a threat not only to their countries, it is a threat to the better establishment of the rule of law, as opposed to blackmail, in Iran, the Middle East, Sudan, Zimbabwe, the world.

If not stopped, Russian imperialism will overreach in the future as it has in the past. For Mr. Putin the irony would be if NATO membership for Georgia and Ukraine, the idea of which he so despises, were by his own conduct proven the only assurance of their freedom.

David A. Mittell Jr. is a member of The Journal’s editorial board.