The annual joint South Korean and U.S. exercises dubbed "Key Resolve" last month for the first time practiced deploying more than 100,000 South Korean troops in North Korea to stabilize the country in case of regime collapse.
The two countries "practiced deploying a large contingent of troops to bring stability in the North in case of civil war in the wake of sudden change there," a government source said on Thursday. "Seoul and Washington practiced preparing for sudden change in the North for the first time during last year's Key Resolve drill, but this was the first time we went on the assumption that South Korean troops would be deployed in the North."
This year's exercise supposed that civil war breaks out due to conflict between hawks and doves in the North Korean military. It envisioned deploying several South Korean Army corps south of Pyongyang to bring hardliners under control and stabilize the North.
A few years back, the two countries' militaries formulated a contingency plan for six scenarios of sudden change in the North -- a coup, civil war, a mass exodus of North Koreans, a massive natural disaster, and kidnapping of South Korean citizens by the North. But they did not stage a drill on the specific assumption of civil war for fear of upsetting the North.
"We conducted the drill this time because top military leaders in South Korea and the U.S. concluded that nobody knows what scenario will materialize because the regime of new leader Kim Jong-un is still unstable," the source added.
Seoul is reportedly worried that North Korean military hardliners have strengthened their position since former leader Kim Jong-il's sudden death late last year.