South Korea and the United States began a joint large-scale military exercise on Monday aimed at bolstering their defense and preparedness against North Korea"s evolving nuclear and missile threats.

The annual Ulchi Freedom Shield exercise, which will last for 11 days until August 31, will include about 30 field training events based on an all-out war scenario, according to an official from South Korea’s Joint Chiefs of Staff. The number of drills this year will exceed those in previous joint military exercises.

The exercise comes as South Korea, the US and Japan remain on alert over North Korea. The South Korean spy agency told lawmakers last Thursday that Pyongyang is preparing various provocations including an intercontinental ballistic missile test timed to coincide with the exercise.

A spokesman for the JCS said the latest drills are “designed to be a tough and realistic exercise to strengthen the combined defense posture and alliance response capabilities based on scenarios that reflect diverse threats within the security environment”.

South Korea and the United States will conduct a number of large-scale complementary training events to increase combat readiness, according to the militaries of the two allies.