A nuclear-powered submarine from the United States arrived in South Korea on Friday, June 16. The USS Michigan’s arrival at the southeastern port city of Busan was the first of its kind in six years.

The submarine is one of the biggest in the world. It can be armed with 150 Tomahawk missiles with a range of about 1,550 miles, and is capable of launching special forces missions.

With the arrival of the submarine, the U.S. and South Korean navies can conduct drills on boosting their special operation capabilities. The South Korean Defense Ministry did not say how long the USS Michigan would stay in South Korean waters.

The arrival of the submarine is part of a recent bilateral agreement between South Korea and the U.S. on enhancing “regular visibility” of U.S. strategic assets to the Korean Peninsula. On Thursday, June 15, the two countries performed joint live-fire drills near South Koreas border with North Korea. The drills were the latest step in countering the growing threat of North Korea’s advancing nuclear program.

“It is false peace when you depend on the enemy’s good faith. The real peace is when we defend our national security with our own strengths,” South Korean President Yoon Suk Yeol said Thursday. “Only a strong military — which can fight and defeat the enemy and which the enemy can’t even dare to challenge – can guarantee the freedom, peace and prosperity of the Republic of Korea.”

In response to the live-fire drills, North Korea fired two short-range ballistic missiles off its east coast. They were the first weapons North Korea launched since it tried to put its first spy satellite into orbit in late May. 

“These launches are a clear violation of multiple U.N. Security Council resolutions, and they demonstrate the threat of DPRK unlawful weapons of mass destruction and ballistic missile programs pose to the region, to international peace and security, and to the global nonproliferation regime,” State Department spokesperson Matthew Miller said Thursday. “I will also note that today the United States imposed sanctions on two DPRK individuals for supporting the DPRK’s unlawful weapons of mass destruction and missile program.”