Kremlin leaders were split on the issue, with military officials objecting most strenuously. Even Putin's closest aides lined up on different sides. The public, according to opinion polls, sympathized with the Americans over the Sept. 11 terrorist attacks but wanted Russia to stay out of any military response.
Yet Putin chose last week to offer President Bush support that would have been unthinkable not just in Soviet times, but even in the Boris Yeltsin era. The most significant: Moscow will not block the former Soviet republics of Central Asia from opening their territory to U.S. forces.
Skeptics say the Kremlin initiatives do not herald a major shift in U.S.-Russian relations. Putin's commitment to Bush, they point out, is limited.
Russian forces will not fight alongside U.S. soldiers in Afghanistan. Russia, the Kremlin says, will not even let U.S. warplanes use its airspace.
Others contend that Putin is engaged in more than a temporary courtship of convenience. He gives Bush important diplomatic backing as the White House tries to fortify its international coalition against terrorism. He gives enough on the military side to be useful.
Perhaps most important, Putin shows Washington and the world that he is willing to discard the rules of the Cold War.
Beyond the Cold War
"We talk of partnership, but in reality we have never trusted each other," Putin said last week in Berlin, speaking to Germany's lower house of parliament. "We are not free of certain cliches and stereotypes from the Cold War. The Cold War is over. . . . The world has become more, much more complicated."
So far, Putin has pulled off his complicated bargain with little protest at home. By not committing Russian troops or territory, Putin has mollified the many conservatives in Russia's military and political leadership.
"The important thing in the president's speech is that Russia's armed forces will not be dragged into war," said Gennady Seleznyov, who leads the lower house of parliament.
Putin is lining up with the West partly because he has few other choices and partly because he expects Russia's support to pay off down the line. Should Putin take this road of cooperation to the end, the West and in particular the United States could offer Russia many rewards.
NATO expansion to the east could be halted indefinitely. That would address Moscow's objection to seeing NATO absorb the former Soviet republics of Estonia, Latvia and Lithuania. Or NATO could speed its expansion to include Russia within a few years. Before Sept. 11, most people dismissed such an idea.
The Bush administration's stated plans to withdraw from the Anti-Ballistic Missile Treaty, which Russia wants to protect as a cornerstone of arms control, also could be stalled.
Russia's foreign debts could be rescheduled, as the United States recently announced it would do for Pakistan.
Chechnya may be a harder issue to resolve. Russia feels its military response to the separatist rebellion has been justified. Some Europeans have softened their criticism of Russian action in the last two weeks, but the United States is hesitant to back off. Besides the human-rights questions, the U.S. contends that the Russian response is creating more terrorists, not wiping them out.
Warplanes in back yard
The most significant aspect of Putin's support for Bush was clearing the way for U.S. warplanes in Central Asia.
Technically such a decision should have little to do with Russia. Uzbekistan, Kazakstan, Turkmenistan, Kyrgyzstan and Tajikistan are independent nations. But to varying degrees, Moscow continues to hold sway over each.
In the end, it was Putin as much as those Central Asian leaders who invited into Russia's back yard the longtime archenemy of Russian generals.
"Imagine if Russian troops came into Mexico," said Michael McFaul of the Carnegie Endowment for International Peace in Washington. "This is a big, big step. The center of gravity in the world has changed."
In some ways Putin had little choice. Some of the five Central Asian nations, such as Uzbekistan, already had told the United States that they would consider such a deployment.