If I were really cynical, I'd suspect some bureaucrats at NATO headquarters in Brussels are secretly glad about the crisis in Ukraine. Why? Because it gives the aging alliance something to do. This motive may also explain why hawkish Secretary-General Anders Fogh Rasmussen seems eager to defend Ukraine right down to the last Ukrainian and why the NATO members that lie closest to Russia are both worried by recent events and pleased that the rest of the alliance is finally paying attention to their concerns.

In fairness, NATO's survival after the Cold War remains something of an anomaly. Alliances normally arise in response to threats, and many previous alliances collapsed quickly once the external danger was gone. Mindful of this tendency, NATO's proponents have been searching for a convincing rationale for its continued existence ever since the Berlin Wall fell. But their efforts have been mostly stillborn; despite annual summits, earnest communiqués, and a lot of brave rhetoric, the alliance's capabilities, importance, and coherence have been visibly declining for two decades.

Things might have been different if the various "out-of-area" missions NATO took on had gone swimmingly, but they didn't. The Bosnian intervention in 1995* and the war in Kosovo in 1999 were at best partial successes; they took longer, cost more, and produced more ambiguous results than NATO's defenders like to admit. NATO's efforts in Afghanistan have been mostly a failure, and no member of the alliance wants to do anything like that again. The Libyan debacle now looks like a monument to Western hubris, even though its architects remain loath to admit just how wrong they were. The United States has been trying to "rebalance" to Asia in recent years -- an arena where NATO has little role to play -- and has been coping with the aftermath of George W. Bush's foolish attempt to "transform" the Middle East. Until the Ukraine crisis arose, NATO looked like a nearly extinct dodo that had somehow managed to last into the 21st century.

Yet NATO survived. This is partly because the alliance was heavily institutionalized, and no bureaucracy goes out of business without a fight. Its persistence also gave the United States some residual leverage in Europe and allowed Washington to pretend that its activities elsewhere had broad international support. Military bases in Europe and a long history of cooperation also facilitated U.S. interventions in other areas and didn't require Europeans to do much in return. Finally, liberal internationalists embraced NATO (and EU) expansion as a way to spread democratic institutions and values into the former Soviet empire, toward the ever-elusive goal of "one Europe, united and free."

But as George Kennan, Michael Mandelbaum, and other experts warned in the 1990s, NATO expansion turned out to be a fundamental strategic misstep. It alienated Russia without making NATO stronger; on the contrary, expansion involved extending security guarantees to mostly weak countries that would be the hardest to defend should Russian power ever recover. Instead of sticking with the early 1990s Partnership for Peace, an initiative that provided many of the same benefits as NATO expansion -- including military-to-military contacts, security dialogue, and support for civil society -- but also included Russia, Washington succumbed to hubris and decided to add to its defense burdens without getting much in return.

Undertaken, like the old British Empire, in a "fit of absentmindedness," NATO expansion rested on the assumption that these various guarantees would never need to be honored. It was not until the brief Russo-Georgian war of 2008 that a few Washingtonians (and a larger number of Europeans) begin to recognize that these commitments might actually involve some cost and risk. But by then it was too late, because any challenge in Eastern Europe would be seen as a test of U.S. credibility and NATO's resolve. Needless to say, this is precisely how most people -- including President Barack Obama, who has called the Ukraine crisis a "moment of testing" -- are now interpreting the tussle over Ukraine.

Yet even the current crisis cannot fully reconcile NATO's fundamental strategic problems. Even if one adopts a worst-case view of Russian intentions, today's Russia is nowhere near as threatening as the old Soviet Union. The USSR was a continent-sized superpower with a larger population than the United States and an economy roughly half as large; today's Russia is smaller and less populous, and its economy is roughly one-fifth the size of America's. The USSR outspent the United States on defense during most of the Cold War, but Russia today is a pipsqueak by comparison. Its only appealing products are oil, natural gas, and raw materials, and it no longer boasts an ideology that can rally supporters worldwide. It can be a regional spoiler and a local troublemaker, but it is not and will never again be a true peer competitor.

These realities also mean that Russia does not threaten the vital interests of most of Europe or the United States. It is a genuine threat to Ukraine's well-being, and it is also a potential problem for the small Baltic states, but Europe no longer has to worry about 90-plus divisions massing on the inter-German border. That's a very good thing, but the lack of a serious strategic threat is also why NATO has trouble marshaling the level of coherence and commitment that it did during the Cold War.

In fact (and in sharp contrast to the post-World War II period), Europe now has the latent wherewithal to deal with the Russian bear all by itself, if only it could get its act together. NATO's European members are notoriously reluctant to spend money on defense or create effective military forces, but it's not because they lack the basic resources. Even today, NATO Europe spends four times more on defense each year than Russia does. If these states were really worried, you'd think they would coordinate their activities more effectively, devote more money to the problem, and spend the existing amounts more efficiently, instead of maintaining militaries that are long on creature comforts and short on fighting capacity

The real challenge NATO faces is the classic dilemma of collective action, made all the worse by the modest nature of the threat to which NATO is now trying to respond. This problem is why NATO's new members are working overtime to convince others -- and especially Americans over in the Western Hemisphere -- that Russian President Vladimir Putin is History's Greatest (or Latest) Monster. If you're Estonian, Latvian, Lithuanian, or even Polish, you don't want to rely on British or French or Spanish help if trouble arises with Moscow. You want to make sure the White House is on your side, and you want hotheads like Joe Biden and John McCain calling for the United States to do everything it can. So these states (and countries like Georgia) spend a lot on lobbying politicians in Washington in order to convince Americans to care as much about their homelands as they do.

Unfortunately, the history of the past 50 years tells us that the more security Uncle Sam provides to others, the less the recipients will do for themselves. Confirmed Atlanticists like the late Richard Holbrooke liked to say that the United States was a "European power," but a momentary glance at the globe shows you that this is nonsense. America is located in the Western Hemisphere, folks, and the extent of its interests in Europe depend on circumstances. When a peer competitor emerges and threatens to dominate the continent, then America's vital interests are fully engaged. When no such rival exists (or when potential peer competitors are located elsewhere), U.S. interests are much reduced. Everybody knows or suspects this, of course, no matter how fervently U.S. officials proclaim their undying support for areas where few vital interests reside.

So what will NATO do at this week's summit? It has already announced plans for a new rapid-reaction force, and Obama has delivered a typically stirring speech pledging U.S. support for all the countries that managed to get themselves into the alliance before anyone thought too hard about the wisdom of this step. There will be the usually pious declarations about enhancing defense capabilities, and a new set of exercises will be planned, provided they don't cost too much. But eventually the war fever will break, and NATO Europe will return to its enfeebled military condition and diplomatic disarray.

Meanwhile, what about Ukraine? In theory, NATO could make a real contribution by forming a united front in favor of genuine diplomacy, something Germany seems especially eager to pursue. By "diplomacy," I mean a process of principled but flexible bargaining whose goal is to resolve the current crisis in a way that gives the various parties what they most need, instead of trying to obtain everything they might occasionally dream about. That process has to begin by recognizing that 1) Russia sees Ukraine's political alignment as a vital interest, 2) it has various cards to play to advance its goals, and 3) it is willing to wreck the country to prevent it from joining the West. You don't have to like those facts -- who would? -- but effective statecraft must begin by acknowledging unpleasant realities. As with most diplomatic efforts, the United States and Europe aren't going to get everything they want and should concentrate instead on getting what is most important.

As I've said before, the best possible outcome here is an agreement that reaffirms Ukraine's independence and sovereignty, ends the fighting, removes any Russian troops on Ukraine's territory, and guarantees Ukraine's status as a neutral buffer state. The status of Crimea is trickier, and I fear it won't be possible to get Russia to disgorge it. We may have to accept that change as the price Ukraine and the West must pay for our prior carelessness. To advance the ball, NATO's leaders should support Ukrainian President Petro Poroshenko while simultaneously discouraging him from upping his demands. In particular, they should make it clear that their support is conditional on Ukraine cutting a reasonable deal. It's a bit like the conditional support the United States provides to Taiwan: The United States will defend that country if its independence is threatened by external military action, but all bets are off if Taiwan provokes trouble by crossing Beijing's "red lines."

Is this a perfect result? Hardly. But it is a lot better than prolonging the crisis, which will damage the still-fragile EU economy, poison East-West relations even further, and do further harm to Ukraine itself. I see little evidence that U.S. officials are thinking along these lines, but perhaps some of America's European partners can convince them otherwise. Isn't that what summit meetings are for?

*Correction, Sept. 5, 2014: NATO's intervention in Bosnia happened in 1995. An earlier version of this article said the year was 1996. (Return to reading.)

Photo by ALAIN JOCARD/AFP/Getty Images