PACIFIC OCEAN (Dec. 10, 2010) The Los Angeles-class attack submarine USS Houston (SSN 713) leads a formation of ships from USS George Washington (CVN 73) Carrier Strike Group and Japan Maritime Self-Defense Force (JMSDF) for a photo exercise during the final day of Exercise Keen Sword 2011. The exercise enhances the Japan-U.S. alliance which remains a key strategic relationship in the Northeast Asia Pacific region. Keen Sword caps the 50th anniversary of the Japan - U.S. alliance as an "alliance of equals." (U.S. Navy photo by Mass Communication Specialist 3rd Class Adam K. Thomas)