Secretary of State Hillary Rodham Clinton is heading to a meeting of NATO ministers in Estonia at a time when the 61-year-old organization is suffering from a kind of mid-life crisis.
Almost 20 years after the collapse of the Soviet Union, the 28-member North Atlantic Treaty Organization is in the midst of an intense self-examination, trying to rethink its basic purpose.
NATO was founded to blunt the long-extinct threat of a Soviet invasion of Western Europe.
Now it finds itself divided on many fronts: doubts among some members about its combat mission in Afghanistan, unease with the continuing presence of U.S. nuclear weapons in Europe, prickly relations with Moscow and concerns about the wisdom of expanding NATO deeper into Russia's backyard.
Clinton and 27 of her NATO counterparts will gather Thursday in Tallinn, capital of the former Soviet state of Estonia, where they're expected to take stock of the alliance and the challenges it faces.
Among the most difficult issues on the agenda are NATO's outlook for success in Afghanistan and the prospects for putting the Balkan nation of Bosnia on track toward NATO membership.
The foreign ministers also are expected to debate the future of the U.S. nuclear umbrella for Europe, which boils down to a question of whether to withdraw the remaining Cold War-era U.S. nuclear weapons there.
The Tallinn meeting, in fact, could split over the question of whether it's time to remove an estimated 200 U.S. nuclear bombs that remain at six air bases in five NATO countries.
The Obama administration hasn't taken a public position on the fate of this small but politically nettlesome nuclear arsenal. Administration officials say NATO should debate the matter and make a collective decision.
But the U.S. is trying to persuade Russia to match any Western reductions of these short-range nuclear weapons with cuts of its own. Some in Europe, including the Germans, are less certain that such linkage is needed.
The meeting also is likely to review progress in rewriting what NATO calls its "strategic concept," updating its mission statement for the first time since 1999.
That document predated the Sept. 11 attacks, the wars in Afghanistan and Iraq and the August 2008 conflict between Russia and Georgia, which is eagerly pursuing NATO membership.
A final draft spelling out NATO's new mission is to be endorsed when President Barack Obama and other alliance leaders meet in November.
U.S. relations with Europe have deteriorated in recent years, in part due to opposition inside the alliance to the U.S. invasion of Iraq in 2003.
One of Obama's main foreign policy goals upon entering the White House was to repair ties with Europe, while also "resetting" relations with Russia, which regards NATO expansion as a threat to its influence in the former Soviet Union.
There is no serious talk inside NATO of dismantling the alliance but, as analyst Stephen Flanagan of the Center for Strategic and International Studies put it in an interview, "Some are questioning what it's for."
The original purpose was framed in purely defensive terms: to protect Western Europe from a potential land invasion by the USSR.
Today there is no USSR, and no credible military threat to NATO as a whole. But the Russia-Georgia war served as a reminder to other former Soviet republics that are now NATO members - like the Baltic states of Latvia, Lithuania and Estonia - that their neighborhood is still dangerous.
NATO's Western European members, including Germany, are more likely to view Russia as a major trading partner and source of natural gas and oil.
Central and eastern European members of the alliance view Russia more uneasily because of Moscow's history as an imperial power. The new members of the NATO club tend to see the alliance's nuclear arsenal as a counterbalance to Russia's military might.
Anders Fogh Rasmussen, the NATO secretary-general, thinks the organization should work more closely with other military alliances far beyond Europe's borders - to include rising powers China and India. He says the Afghanistan war experience has shown the need for such global linkages.
"But some fear NATO stretching itself too thin," he told a University of Chicago audience on April 8. "Others are afraid that NATO wants to rival the U.N. For these reasons, among others, there is hesitation about NATO engaging more systematically with countries like India or China."
Cybersecurity is emerging as a major worry for NATO, and Estonia is a fitting venue for discussing this emerging threat.
In April and May 2007, during heightened tensions between Russia and Estonia, hackers unleashed a wave of cyber attacks that crippled dozens of Estonian government and corporate sites in one of the world's most wired countries.
Estonian authorities traced the attacks to Russia and suggested they had been orchestrated by the Kremlin - a charge Moscow denied.
Adm. James Stavridis, the top NATO commander in Europe, says the 2007 case - and the prospect of others to come - poses a hard question for the alliance.
The NATO credo of "an attack on one is an attack on all" is the fundamental pledge by all signatories to the NATO founding treaty. But does a cyber attack against one NATO member compel the alliance as a whole to come to that country's defense?
"In 1949 when the treaty was written, no one could have conceived this cyber world," Stavridis said in a Feb. 2 speech.
"In NATO in particular, in my view, we need to talk about what defines an attack ... because in this unsettled sea in which we sail, I believe it is more likely that an attack will come not off the bomb rack of an aircraft but as electrons moving down a fiber optic cable."
While the meeting is expected to focus on security issues, some see the upcoming meeting in Tallinn as, in part, a chance for a little marriage counseling.
Finnish Foreign Minister Alexander Stubb says the meeting could help the U.S. and its European allies air pent-up frustrations and ease tensions. "I feel it is time for the grumpy old Atlantic couples to renew their wedding vows," he said.
This program aired on April 21, 2010. The audio for this program is not available.