A top U.S. commander said Thursday the recently concluded joint U.S.-South Korea military exercises were a good first step for Seoul to rehearse a scenario in which it is set to play a leading role in defending itself.

Amid heightened North Korean war rhetoric, South Korea and the U.S. ended a 10-day military exercise, code-named Key Resolve.

About 10,000 South Korean and 3,000 U.S. troops took part in the largely computer simulated war games.

The annual exercises were the first of their kind in which South Korea's military played a primary role as it prepares to take over the wartime control of its troops from the U.S in 2015. South Korea's wartime military control has so far been under the purview of the top U.S. commander in the country.

Lt. Gen. John Johnson, the 8th U.S. Army Commander, said the joint exercises, which were planned and executed by South Korea's office of Joint Chiefs of Staff (JCS) for the first time, were a success.

"This is the first major exercise that ROK JCS has planned and conducted. We did everything we needed to do for training. The opportunity to get together was excellent," Johnson told Yonhap News Agency during a visit to the Warrior Base in Paju, a South Korean town close to the border with North Korea.

The ROK, or the Republic of Korea, is the official name of South Korea.

U.S. military officials said that about 2,500 of American troops who took part in the exercises came from Hawaii. Also taking part from the U.S. were U.S. B-22 bombers and a nuclear attack submarine.

Johnson said the allies have been making good progress to develop an alternative command structure to replace the Combined Forces Command in a way that can ensure military readiness. The CFC is expected to be dissolved after Seoul regains wartime operational command control (OPCON) from Washington in December 2015.

"We've been working on that plan for a long time. We are able to do things we need to do. I think we made progress," Johnson said.

Regarding conservatives' calls to delay the planned transition in the wake of growing missile and nuclear threats posed by North Korea, Johnson said the decision is up to the leaders of the two nations and the transition preparations have been "on plan."

"We always rehearse scenarios, and these exercises give opportunities for us to work together and execute those plans to allow us to defend the ROK (Republic of Korea) and U.S. alliance," he said, referring to South Korea's official name. "We will practice before it's time to conduct the OPCON transition to make sure that we're ready."

(Yonhap News)