The drill runs from Monday to Friday and began at Namhan River in the city of Yeoju, almost 39 miles southeast of Seoul and 71.4 miles from the border with North Korea, the Yonhap news agency, citing the South Korean armed forces.
The exercise involves 590 troops, 243 vehicles and aircraft, including K1A2 tanks, K808 armored vehicles and H-47D helicopters.
During the drill, the US and South Korean troops built a 918-foot pontoon bridge in three hours, which allowed the vehicles to cross the river, reaching the exercise's destination.
In May, South Korea held major three-day drills to practice defending its islands in the Yellow Sea near its border with North Korea, which for the first time in seven years involved simultaneous shooting and landing operations. The drills took place off the islands of Baengnyeongdo, Yeonpyeong and Daecheongdo.
The 2018 inter-Korean military agreement banned regiment-level field maneuvers or those by larger units near the border, but both Seoul and Pyongyang resumed drills in the contested areas of the Yellow Sea after the accord collapsed in 2023.