Less than two years ago at NATO’s Lisbon summit, the Alliance adopted a new Strategic Concept intended to chart NATO’s course for the coming decade. Yet since then, the members of the Alliance have weathered a dramatic financial crisis, precipitating deep cuts in defense. NATO succeeded in Libya, but faces continuing challenges in Afghanistan. Many allies hanker for the good-old-days, an Alliance more focused on traditional collective defense, while others believe the best course would be for the transatlantic Alliance to serve as a force for global security and stability, together with regional actors, as it did in Libya.

NATO,...

It was the shot heard around the Alliance.

In a hard-hitting farewell speech delivered in Brussels just days before his retirement as US Secretary of Defense on July 1, 2011, Robert Gates offered a tough-love message to America’s NATO allies. He warned that future US policymakers, and the American public, would lose interest in the Alliance if Europe and Canada failed to make the investments and tough political choices needed to remain America’s ‘go-to partners’ for global challenges.

This May, leaders of the twenty-eight NATO allies will gather in Chicago for the first US-hosted NATO summit since 1999. The summit...