South Korea and the United States have officially launched a combined staff of their wartime joint division to be tasked with military operations in case of war, military officers here said Friday.

In September, the allies agreed to establish a combined wartime division of their allied troops in early 2015 to enhance their joint defense posture and "tactical-level" combat capabilities to better deter a belligerent North Korea.

"Thirty South Korean officers were dispatched to the joint staff office Thursday and began serving their duty along with 30 officers from the U.S.," a military officer here said, requesting anonymity.

The newly launched joint staff was created as part of the U.S. 2nd Infantry Division, currently located in Uijeongbu, just north of Seoul.

"Maj Gen. Thomas S. Vandal, who currently heads the 2nd Division, leads the joint staff and South Korean Brig. Gen. Ahn Sung-hwan took the deputy commander position," the officer added.

During wartime, the joint staff will control the 2nd Infantry Division and a South Korean-mechanized infantry brigade, which will carry out normal duties in its assigned area during peacetime, according to Seoul's defense ministry.

The division's wartime operations involve launching civil affairs operations and special ones, such as eliminating weapons of mass destruction, another Seoul officer said.

"It is the first time ever in the world that two nations have organized a combined division," said the officer. "The formation helps Seoul and Washington strengthen interoperability and boost their joint posture by having more opportunities to stage joint drills to better prepare for war."

The U.S. infantry division and South Korea's 16th brigade plan to hold a joint military exercise next week to check and boost their joint readiness posture and to take part in the allies' major annual Key Resolve drill, set to begin in March, he said.

The joint unit, meanwhile, will be moved to Pyeongtaek, some 70 kilometers south of the capital, by the end of next year, along with the 2nd Division, in accordance with the base relocation plan in South Korea, according to the defense ministry.

Seoul and Washington have been working to relocate the Yongsan Garrison, the sprawling U.S. military headquarters in central Seoul, and the 2nd Division north of Seoul to Camp Humphreys in the city of Pyeongtaek with a plan to turn the Seoul areas into vast public parks.

About 28,500 U.S. troops are currently stationed in South Korea, a legacy of the 1950-53 Korean War. (Yonhap)