NATO's midlife crisis

The signs of turning 50 seem universal. It's often a time to re-evaluate goals, examine the past and plan once again for the future. And as the North Atlantic Treaty Organization turns 50, it is no different.

• Why it matters: How Kosovo is redefining NATO

NATO's shifting role

On April 4, 1949, 12 nations signed a treaty in Washington, D.C., creating a defense alliance known as the North Atlantic Treaty Organization.

NATO wannabes

Many of the countries seeking NATO membership are doing so for reasons of protection.