Seven countries including the U.S., Thailand and South Korea kicked off a joint military exercise, "Cobra Gold 2011," in Thailand on Tuesday.

This year, seven nations --- including Japan, Singapore, Indonesia and Malaysia --- have dispatched a combined 14-thousand troops to the exercise.

South Korea had been an observer of the exercise until it first participated last year, when South Korea sent 330 Navy and Marine Corps members and landing vessels to the drill.

Given security conditions at home, including North Korea's shelling of a South Korean island late last year, Seoul will send one Marine Corps platoon of 56 members to the seven-nation drill this year.

Cobra Gold is the largest defense drill in the Pacific region. It began in 1982 as a bilateral exercise between the U.S. and Thailand.