On April 3, the leaders of history's most successful multilateral alliance will gather in Strasbourg, France. NATO confronts an existential crisis in Afghanistan, which has become a test of its utility in the twenty-first century. If it fails there, it risks fading into irrelevance.

Today, fifty-five thousand troops from thirty-eight nations-including twenty-three thousand from the United States-are fighting under NATO's banner. (Another twenty thousand fall under a separate U.S. command as part of Operation Enduring Freedom.)

President Obama will soon announce the results of a two-month strategic review of U.S. Afghan policy. The administration will embrace a ramped-up counterinsurgency effort, beginning with seventeen thousand more U.S. troops. The success of this "made in the USA" strategy, however, will require an international unity of effort. Unfortunately, America's allies remain divided on some fundamental issues. Before the Strasbourg summit, NATO needs to answer the following questions.

Whose war is this? In 2002, German Defense Minister Peter Struck memorably declared that the defense of Germany began in the Hindu Kush. This unity of purpose has since evaporated. Public support for the war is plunging across most NATO countries, and even previously committed nations like Canada and the Netherlands plan to reduce their military presence. Allied governments have placed more than seventy "national caveats" on involvement in combat operations-content, as British Defense Secretary John Hutton has noted, to "freeload" on the U.S. military. The Strasbourg summit must clarify whether this is still NATO's war-or just America's.

What is the end state?  President Obama has wisely dialed down the sweeping rhetoric of the Bush administration, which created unrealistic expectations about what the international community could hope to accomplish in Afghanistan. As the president concedes, Afghanistan is unlikely to emerge soon as a prosperous, effective democratic nation. What Obama has not done is to communicate a desired end state there, beyond the minimalist goal of depriving al-Qaeda of a safe haven. Some NATO allies, as well as the United Nations and World Bank, remain committed to long-term state-building as a solution to chronic Afghan insecurity and abysmal governance, but Washington appears to be moving in the opposite direction. The Strasbourg summit must define a realistic trajectory for the mission through 2020 that the international community can support.

What is the mission? The lack of a clear end state makes it even harder to reach consensus on what NATO's mission should be, to say nothing of the appropriate division of labor in fulfilling it. Washington's emerging strategy envisions a robust counterinsurgency campaign to separate the Afghan population from the Taliban, targeted counterterrorist operations against al-Qaeda, and a vigorous counternarcotics effort to cut the taproots of corruption and violence. Few U.S. allies are enthusiastic about these tasks, preferring to focus on traditional peacekeeping and reconstruction. Washington and its partners need to agree on the right balance among these diverse activities-and national responsibilities for carrying them out. If Europeans decline to fight, they must be prepared to "surge" on the civilian side, deploying aid and experts to train Afghan security forces and address the country's glaring governance and economic gaps.

What is the political process? History-not least the Vietnam experience-suggests that no counterinsurgency strategy can rescue an illegitimate and dysfunctional regime. Insurgencies can only be defeated politically, not militarily. Unfortunately, President Hamid Karzai and the entire Afghan government are increasingly reviled by the population, thanks to the impunity enjoyed by powerful warlords and the corrupting impact of the drug trade. NATO must advance a realistic political strategy to complement its military one. One essential prong in this approach is demanding better Afghan government performance in fighting corruption. Another is supporting Afghan-led negotiations with "moderate" Taliban. NATO allies must speak with one voice on both of these contentious issues.

What can be done about Pakistan? Finally, NATO must adopt a common approach to Pakistan, where Taliban leaders continue to find sanctuary and fertile ground for recruiting foot soldiers. The Afghan insurgency will only end when Pakistan eliminates the Taliban's havens, not only in the Federally Administered Tribal Areas, but also in Baluchistan. And yet many NATO allies, fearing entanglement in Pakistan's political troubles, would prefer to treat the International Security Assistance Force mission as a purely Afghan affair. To broaden NATO's horizons, Washington should champion and seek allied support for a regional approach, one that gives Pakistan assurances of its territorial integrity in return for cracking down on sanctuaries and infiltration.

When the cold war ended two decades ago, the alliance was told to go "out of area or out of business." Like it or not, NATO's continued relevance depends on whether it can address the challenges of irregular warfare and the dilemmas of failed states.  If the alliance rises to the occasion in Afghanistan, it will remain a pillar of U.S. and international security. If it fails to do so, NATO-having gone out of area-may also go out of business.

Stewart Patrick is senior fellow and director of the program on international institutions and global governance at the Council on Foreign Relations. He had lead responsibility for Afghanistan issues on the State Department's policy planning staff from 2003-2004.