NATO's largest mission is coming to an inglorious end. Offcially, the alliance still claims that 2014 is the year it will disentangle itself from Afghanistan. Even before the recent bloody incidents, however, key members of the alliance were talking about an earlier departure. The violence sparked by revelations of Koran burning and the murder of Afghan civilians by a U.S. soldier have sapped  already low levels of trust between the alliance and its Afghan partners and made an early exit more likely.

What happens to Afghanistan--and to the region--after NATO's departure is the most obvious question. But the alliance's coming retreat from Kabul raises another issue: what happens to NATO after its largest mission ends? Since  shortly after the Cold War, and notwithstanding predictions of its demise, the Western alliance has been in a frenzy of activity: it expanded to take in almost a dozen new members; through the Balkans conflicts, it developed a new speciality as a regional stabilization force; it activated its members' Article V committments for the first time in the wake of the 9/11 attacks and a few years later took on the Afghanistan mission.

Barring some new development, however, NATO activity will soon be at its  lowest ebb since the early 1990s. Expansion of the alliance has mostly run its course. The Libya operation is done. The Bosnia stabilization mission, launched in 1995, was handed over to the European Union in late 2004. NATO does still have a mission in Kosovo, but that force is now smaller than 6,000 troops and will probably shrink further. Just as NATO moves into a shiny (and expensive) new headquarters building in Brussels, the world's most successful military alliance may find itself struggling to be relevant.

There are several different scenarios for the alliance:

The Waiting Game: The last two decades suggest that the alliance may not have to wait long before some new military challenge descends on it. While the alliance isn't keen to intervene in Syria, the continuing instability of the Arab Spring may ultimately lead to a new stabilization operation. Parts of the Balkans are still tense and may require new attention. An African mission isn't out the question. On this view, all the alliance really needs to do is oil the wheels of military cooperation and stand ready.  For all its fissures and tensions, NATO  still brings together most of the world's most advanced militaries and offers them a ready-made command structure. In an unstable world, it won't be long before that machinery is needed again.

Turn East: Some of NATO's newer eastern and central European members might prefer that the alliance look closer to home for dragons to confront.  Russia is rearming and showing signs of revanchism. It periodically makes noises about placing missiles in the enclave of Kaliningrad. The conflict with Georgia could easily flare up again. In this tense atmosphere, perhaps NATO should return to its original mission: Keeping Europe safe from Russian bullying.

New security threats: NATO's members face a new generation of security threats, from cyberattacks to shadowy terrorist networks. One possible path forward for the alliance would be to develop expertise in these areas and become more than a provider of stabilization forces. This would require a major reorientation; the alliance is not well placed to address these more nebulous threats. It doesn't operate drones or do much with special forces. Its national interlocutors are defense ministers, not intelligence agencies or interior ministries. But there is a need for greater coordination in these areas, and NATO could prove to be a convenient and familiar forum.   

Go Global: Back in 2005, the current American ambassador to NATO, Ivo Daalder, wrote an article with James Goldgeier arguing that NATO's future lay outside the alliance's traditional area of operations. What's more, they argued, the time had come for NATO to expand its membership beyond the North Atlantic area. "NATO's next move must be to open its membership to any democratic state in the world that is willing and able to contribute to the fulfillment of NATO's new responsibilities."  The expensive and controversial Afghanistan operation has sapped enthusiasm for this kind of dramatic change, but it remains a potential long-term alternative.    

Slow Fade: Maybe this search for ways to keep the alliance relevant is misguided. After all, institutions and alliances should respond to some felt need; they are not ends in themselves. Commentators of a realist bent--for example, George Will and Steve Walt--have long expected that NATO would come undone in the post-Cold War. The frenetic alliance activity of the last fifteen years has seemed to prove them wrong, but they could see an important long-term reality: that there is no compelling strategic need for the alliance. Without that need, and as the spate of nation-building operations subside, NATO may start a dignified fade into the background.