Los Angeles-class attack submarine USS Tuscon (SSN 770) transits the East Sea July 26, 2010, while leading a 13-ship formation. South Korea and the United States were conducting combined alliance maritime and air readiness exercise Invincible Spirit in the seas east of the Korean peninsula from July 25 through 28, 2010. This was the first in a series of joint military exercises that will occur over the coming months in the East and West seas. (U.S. Navy photo by Mass Communication Specialist 3rd Class Adam K. Thomas/Released)