Russia's military crushing of Georgia confronts the US with a stark choice – whether to challenge Moscow in its own backyard, ortacitly concede its sphere of influence there. Already, however, it has taught Washington a harsh lesson: either way, nothing the US does can make much difference.
Yesterday, Robert Gates, the Defence Secretary and a veteran official who has dealt with Russia and the Soviet Union for 30 years, acknowledged the limits of America's power to influence the behaviour of its former superpower rival.
If Russia did not step back now, relations with the United States could be affected for years to come, he said at the Pentagon. But the aid the US was now sending to Georgia was purely humanitarian, and for the time being would remain so.
He did not rule out broader US help in repairing the damage to Georgia's economy and armed forces. But he saw "no prospect for the use of [US] military force", even in the longer run. "Is that clear enough?" he asked his questioner.
Which raises the most pressing issue: short of force, how can the US "punish" Russia for whatMr Gates said was a calculated, unmistakeable warning from the Kremlin to other former members of the Soviet Union – most notably Ukraine and Moldova – that are entertaining notions of movingcloser to Nato and the West?
The dispatch of humanitarian aid was the bare minimum the Bush administration could do to assuage neoconservative hardliners who demand that Washington draw a line in the shifting Caucasian sands.
All that Mr Gates could specifically point to was the cancellation of various planned military exercises involving the US, Russia and Canada and "a full re-examination" by the Pentagon of its overall relationship with its Russian counterpart.
But the hardliners want much more: a ban on Moscow joining the World Trade Organisation, itsexpulsion from the G8 and a boycott of (or at least moves to undermine) the 2014 Winter Olympics in Sochi, southern Russia, near the border with Abkhazia, a flashpoint in the conflict.
The hardliners insist the US must give no ground in its encouragement of other former Soviet republics to move towards the West – one of the contributing factors to the Kremlin's revenge on the headstrong Georgia. "Realists", on the other, say a new Cold War is not the answer: the clearest lesson of the crisis is that Washington must not promise, or even (as in the case of Georgia) be interpreted as promising, more than it can deliver.
The two approaches have been reflected in the US presidential race. The Republican John McCain, touting his firm and experienced hand in foreign affairs, says Moscow should be given no quarter. "We Are All Georgians Now", was the title of an article he wrote for yesterday's Wall Street Journal.
At the start of the crisis, by contrast, the approach of Barack Obama was more nuanced. He urged Russia and Georgia to show restraint, calling for a diplomatic solution. As the Russian offensive spread beyond South Ossetia into Georgia proper, the Democratic candidate toughened his language. But he indicated what hardliners cannot accept, that little Georgia, too, bore responsibility for the war.