The Wall Street Journal reports:

On the night of March 11, villagers in the Republic of Georgia's mountainous Kodori valley say they heard the distinctive "thwack, thwack, thwack" of low-flying helicopters.

The choppers hovered in darkness for almost two hours, coordinating a ground-and-air attack on three settlements, according to more than 50 witnesses interviewed by United Nations-led investigators. Minutes before they left, a guided missile designed to be fired by helicopters struck a Georgian government building.

No one was killed in the attacks, which were little-noted in the West at the time. But four months later, they look set to cause waves on a global stage as the U.N.-led probe issues a final report on the incident as early as this week. The Wall Street Journal has seen two preliminary reports.

Georgia accuses Russia of authoring the attack in an effort to intimidate the former Soviet republic or bait it into a military response. The two countries have been at sharp odds over Georgia's efforts to join the North Atlantic Treaty Organization and to reclaim Abkhazia and South Ossetia, two separatist areas of Georgia under protection of Russian peacekeeping forces.

Georgia, a strategically important country on Russia's southern border, hopes to bring the matter to the U.N. Security Council in New York. Moscow, which sees NATO expansion as an attempt to contain Russian influence over former Soviet republics, has imposed trade and transport embargoes on Georgia. Russia denies involvement in the March attack and accuses Georgia of orchestrating it in order to create an international incident, a charge Georgian officials reject.

The final report has to be approved by experts from both Russia and Georgia and is likely to reflect the politically sensitive nature of the debate. People familiar with the matter say Russia and Georgia are haggling over one key point: Russia is pushing to include language that indicates there is no hard evidence to conclude that helicopters were even in the area that night, despite the witness testimony.

The sheer sophistication of a helicopter attack in high mountain passes at night would point to Russian authorship. Its military is the only one in the region known to have the equipment and training needed to pull it off. If Russia's involvement is ultimately confirmed, the attack would amount to an extraordinary military strike on a neighboring state.

"If Russia thinks it can bomb Georgian territory and get away with it, that's dangerous not just for Georgia but for all its neighbors -- for Ukraine, for Azerbaijan, for the Baltic states," Georgian Interior Minister Vano Merabishvili said in an interview.

If the report concludes there isn't enough evidence to say helicopters were present, it will leave open the possibility that Georgia attacked itself in an elaborate hoax designed to smear its neighbor. Russia argues that Georgia is trying to gain sympathy for its efforts to reclaim Abkhazia and South Ossetia.

"We don't know if there were any helicopters, but we do know that there could not have been any helicopters from Russia," said Dmitry Peskov, a spokesman for Russian President Vladimir Putin. "Observers have noticed lots of actions of a provocative nature from the Georgian side."

At the heart of the incident in Kodori lie regional politics, history and a looming decision to grant independence to Kosovo, the separatist province of Serbia that in the 1990s suffered an attempt at ethnic cleansing by troops loyal to former Serbian President Slobodan Milosevic.

Like Kosovo, Abhkazia seeks independence. The separatist region lies within Georgia, but most residents have Russian passports, are protected by Russian peacekeepers, speak Russian and spend Russian rubles. The region borders Russia along the Caucasus Mountains.

Russia says if the West recognizes Kosovo as independent -- something Moscow vehemently opposes and Washington supports -- that will set a precedent for other separatist enclaves such as Abkhazia.

Last summer, Georgia installed its own parallel Abkhaz government in the Kodori valley and renamed it Upper Abkhazia, infuriating separatist leaders in the regional capital, Sukhumi.

Abkhaz officials say they have a legitimate claim to independence. When the Soviet Union was formed, Moscow made it a republic, like Georgia. But in 1931, Josef Stalin -- himself a Georgian -- folded Abkhazia into Georgia.

By 1989, the last full census, ethnic Abkhaz made up 18% of the territory's population. When the Abkhaz sought to break away in the early 1990s, Georgia sent in troops who committed atrocities that still rankle deeply in Abkhazia. In the war that followed, the Abkhaz drove out 250,000 Georgian civilians, with help from Chechen and other volunteers from Russia, halving the territory's population and committing atrocities of their own.

"These are ethnic cleansers," Georgian President Mikheil Saakashvili said of the Abkhaz leadership in an interview. Under the pro-Western Mr. Saakashvili, Georgia has pushed back.

Last July, special forces from the Georgian police seized control of the Kodori gorge from the Georgian warlord who for years had run the valley as a personal fiefdom. The seizure enabled U.N. monitors and Russian peacekeepers to patrol the valley for the first time since 2003, when several U.N. personnel were kidnapped in Kodori. But it also broke a cease-fire agreement, under which Kodori was supposed to be demilitarized.

"Their aim was to take the territory and turn it into a bridgehead" for a future attack on Abkhazia, says Sergei Shamba, the pro-Russian territory's de facto foreign minister. "We will not let them live in peace there....When we have no more diplomatic tools, we will resolve this by force."

Georgian officials insist they don't want a conflict, and U.N. inspectors have found no heavy weaponry in the valley. But with Russian peacekeepers in Abkhazia and South Ossetia and the possibility looming that Moscow may recognize the two territories if the West recognizes Kosovo, Georgian leaders are getting increasingly active, and creative, in their efforts to win hearts and minds in the territories.

In Kodori, South Ossetia and nearby, Georgia is building discos, hotels, movie theaters, light shows, schools and hospitals to entice the impoverished Abkhaz and South Ossetians back. Since Georgian police overran the Kodori gorge last July, Malkhaz Akishbaia, the 35-year-old head of Georgia's Abkhaz government, has built two new schools, a bright-pink administration building, a bank, a movie theater and two small hydroelectric plants to provide the local population with power. He has renovated and equipped the local hospital. Ski lifts and a skating rink are planned -- by presidential decree.

Georgian officials say the March 11 attacks were a raw demonstration of Russian power.

The first people who say they heard helicopters, at around 9:10 p.m. on March 11, were villagers at the northern edge of the valley. They said they heard the choppers come from the north (where Russia lies) and go south, toward the villages of Chkalta and Adjara. That would indicate the helicopters entered the gorge through passes from Russia -- or were already hidden in the valley.

After the attack, Georgia submitted its radar records to U.N. investigators. These showed no flights in the area, indicating that any helicopters must have flown to Kodori below radar, shielded by mountain passes. The U.N. also asked Russia to provide its radar logs.

The Russian Defense Ministry response, seen by The Wall Street Journal, wasn't sent until May 25. It said the military records "only flights by aviation of the Russian armed forces." As there were no Russian military flights that night in the area, the letter said, there were no records to provide.