Commodore Robert Wesley's Constitution-class starship, badly damaged by the M-5 computer during the 2268 war games.
The USS Lexington was a Constitution-class starship commanded by Commodore Robert Wesley in the 2260s. In 2268 it led the war-games exercise testing the M-5 computer installed aboard the Enterprise.
When the M-5 began firing full-power phasers at the other ships, the Lexington was badly damaged and lost dozens of crew. Wesley, believing the Enterprise had run amok, was given permission to destroy it, but he held his fire after the M-5 shut down and Kirk left the shields lowered to show the ship was no longer a threat.