The military forces of South Korea and the United States have begun joint live-fire drills based on the scenario of a contingency on the Korean Peninsula.
Citizens were invited to view the drills on Thursday, which showcased the capabilities of the alliance.
The joint exercise is being held at a training field near Seoul. The allies mobilized some 2,500 troops for the drills. Four more drills will be held through June 15.
The drills are based on the premise of a North Korean attack on South Korea. On Thursday, the South's tanks and other armaments practiced bombarding targets on a hillside in coordination with reconnaissance drones.
South Korean and US helicopters and fighter jets practiced attacks on land targets. Special units also descended from helicopters to simulate taking control of enemy territory.
The exercise marks the 70th anniversary of the US-South Korea alliance.
North Korea last Friday condemned South Korea and the US through its state media for planning to start the drills. It said they "are bound to face corresponding responses."