SEOUL - The Republic of Korea (ROK) and the United States launched Tuesday an annual joint military exercise aimed at enhancing their interoperability in defense.

The 10-day computer-assisted command post exercise, dubbed Ulchi Freedom Guardian, brought together some 530,000 ROK and US troops on the Korean peninsula and at US military headquarters in the Pacific and the US, according to the Combined Forces Command (CFC) here.

The US-led United Nations Command has informed the Democratic People's Republic of Korea (DPRK) of the defensive nature of the routine drill, according to the CFC.

The drill is "focused on preparing, preventing and prevailing against the full range of current and future external threats" to ROK and the region, Gen. James D. Thurman, Combined Forces Command Commander, said.

"We are applying lessons learned out of Iraq and Afghanistan, as well as those garnered by the alliance's recent experiences with North Korean (DPRK) provocations on the peninsula and past exercises," he added.

The DPRK demanded last week the allies cancel the joint exercise, which it sees as a plot against Pyongyang.