North Korea has commissioned a second destroyer amid a joint military exercise by the United States, South Korea, and Japan

North Korean leader Kim Jong Un inaugurated the Pyongyang fleet’s second destroyer on Monday and called for the strengthening of a “more reliable” nuclear deterrent, according to state media.

The ceremony took place as the United States, South Korea and Japan began a trilateral military exercise. North Korea considers these maneuvers a direct threat to its security and frequently cites them as justification for developing its military and nuclear capabilities.

The inauguration of the second destroyer represents a new stage in Pyongyang’s efforts to expand and modernize its navy. Kim Jong Un emphasized the need for a more credible nuclear deterrent capability, without North Korean authorities providing, in the reports cited, details about the ship’s armament or performance.