The amphibious dock landing ship USS Tortuga, left, and the amphibious assault ship USS Essex, right, steam alongside the fleet replenishment oiler USNS Rappahannock, with the guided-missile destroyer USS Stethem and the amphibious dock landing ship USS Harpers Ferry close behind, during an refueling at sea, preparing for Cobra Gold 2009. Cobra Gold is an annual Kingdom of Thailand and U.S. co-sponsored military exercise designed to train U.S. and partner Asian-pacific forces. The exercise will include humanitarian projects with participants from Indonesia, Japan, Singapore, Thailand and the U.S.