The Cold War left a nuclear landscape whose remnants must still be sensitively managed. As NATO grapples with the future of its deterrence posture, it faces the contentious question of whether reducing or withdrawing forward-based U.S. nuclear weapons in Europe would unacceptably reduce the security of its member states. The weapons were intended to promote nuclear burden sharing through an Alliance-wide decision process. But the European aircraft that would drop them are aging and will need replacement or refitting. Decisions are needed soon on whether this should occur.

The United States favors still greater nuclear restraint, as it declared in its recent Nuclear Posture Review. But it is reluctant to change in Europe without the agreement of all its allies. Some member states, especially on NATO’s periphery, seek the continued assurance that they believe these theater weapons offer. Other allies see the decision as an urgent opportunity to advance the goal of the abolition of nuclear weapons. So the upcoming debate in Lisbon will require a rare combination of determination, political sophistication, and analytical clarity—and issues will likely still require resolution long after the summit.

Although significant differences between member states exist, most agree NATO should:

• Remain capable of launching a nuclear response to aggression or blackmail as long as nuclear weapons exist.
   
• Reassure the most exposed members about the Alliance’s capacity and commitment to defend them.
   
• Avoid a high-profile transatlantic difference of opinion, which would represent the fastest and most farreaching loss of collective credibility.
   
• Contribute to the reduction and, when possible, the elimination of nuclear weapons in the world.

To foster lasting consensus on the future shape and basing of nuclear deterrence, NATO’s leadership must pay close attention to the internal political pressures within key member states, as well as others’ perceptions of external insecurity. Both result from long-term geographical, historical, and cultural factors. A good decision on nuclear arrangements will safeguard both the Alliance’s credibility and its cohesion—and enable NATO to focus on new and emerging threats without distraction.