Story highlights

300,000 South Korea soldiers to take part in joint military drills

Marines storm beach aboard assault vehicles in a mock amphibious landing

U.S. general says exercises to "deter" North Korea

Pohang, South Korea CNN  — 

Amid blasts of explosives and camouflaging smoke, U.S. and South Korean marines and sailors stormed a beach aboard assault vehicles Saturday in a mock amphibious landing.

The carefully choreographed drill begins a much larger, eight-week series of annual joint military exercises between the U.S. and South Korea.

They take place against a backdrop of growing tension and missile tests just across the Demilitarized Zone in North Korea.

South Korea’s defense ministry spokesman is calling the maneuvers “the largest scale ever,” involving 300,000 South Korean troops and at least 17,000 from the U.S.

Small detachments of forces from Australia and New Zealand also participated in Saturday’s operations.

Heightened tensions