“Let’s be honest, Kyrgyzstan is turning into a collapsing state, or at least part of it is, and what was partially responsible is this geopolitical tug of war we had,” said Alexander A. Cooley, who included Manas in a recent book about the politics of military bases. “In our attempts to secure these levers of influence and support the governing regime, we destabilized these state institutions. We are part of that dynamic.”

Last week, as pillars of smoke rose off Osh and Jalal-Abad, citizens begged for third-party peacekeepers to replace local forces they suspected of having taken part in the violence.

Roza Otunbayeva, the head of Kyrgyzstan’s interim government, asked Moscow for peacekeepers, and when that request was denied, for troops to protect strategic sites like power plants and reservoirs. She asked Washington to contribute armored vehicles from the base at Manas, which she said would be used to transport the dead and wounded, she told the Russian newspaper Kommersant.

So far, Moscow and Washington have responded mostly with humanitarian aid pledges  late on Friday, Russia’s Defense Ministry said that Ms. Otunbayeva’s request was still under consideration.

The United States, overextended in Afghanistan and Iraq, has neither the appetite nor the motivation for a new commitment. Russia, the more obvious player, sees the risks of a deployment outweighing the benefits. Russian troops would enter hostile territory in south Kyrgyzstan, where Mr. Bakiyev’s supporters blame Moscow for his overthrow, and Uzbekistan could also revolt against a Russian presence.

Mr. Vlasov, of Moscow State University, said: “Who are we separating? Uzbeks from Kyrgyz? Krygyz from Kyrgyz? Kyrgyz from some criminal element? There is no clearly defined cause of this conflict. It would be comparable to the decision the Soviet Politburo made to invade Afghanistan  badly thought through, not confirmed by the necessary analytical work.”

If the explosion of violence was a test case for the Collective Security Treaty Organization, an eight-year-old post-Soviet security group dominated by Russia, it seems to have failed, its leaders unwilling to intervene in a domestic standoff. In any case, neither the Russian public nor the county’s foreign policy establishment is pressing the Kremlin to risk sending peacekeepers.