The guided missile submarine USS Michigan will visit the port of Busan, South Korea this weekend for the second time this year, in what is a clear warning to North Korean leader Kim Jong-un. The vessel is a nuclear-powered submarine that can launch more than 150 precision-guided cruise missiles.

The Michigan last visited Busan in late April of this year, at which time North Korean state media reportedly warned "the USS Michigan won't even be able to rise to the surface when it will meet a miserable end and turn into an underwater ghost."

The Michigan's visit comes at a time when the United States is putting increasing pressure on North Korea in response to nuclear and long-range missile tests. Analysts now believe Pyongyang can strike as far as New York City with a nuclear weapon—maybe. In addition to the submarine visits, the U.S. Air Force has repeatedly flown B-1B heavy bombers near North Korea, with the latest flight occurring earlier today.

The Michigan is unique among submarines in that its primary armament isn't torpedoes but conventionally armed cruise missiles. The end of the Cold War and arms control treaty limits made four of the U.S. Navy's 18 Trident missile submarines redundant. Rather than retire the submarines, the Navy converted them into cruise missile submarines, taking the hull space devoted to 24 Trident II D-5 nuclear ballistic missiles and reworking it to house 22 Multiple-All-Up-Round Canisters, each loaded with seven Tomahawk land attack cruise missiles.

The result is a single sub that carries 154 cruise missiles, each of which can travel up to 900 miles and attack a target with a 1,000-lb. high explosive warhead with GPS-level accuracy. The Michigan is an incredible package of precision firepower that rivals the destructive power of a full-sized aircraft carrier. Two converted submarines, Michigan and Ohio, serve with the U.S. Pacific Fleet.

Sea-launched cruise missiles have become a major tool in the toolbox of modern warfare. US submarines have launched several cruise missile strikes, starting with Operation Desert Storm in 1991. In 2011, the Michigan's sister ship USS Florida launched 90 cruise missilesagainst targets in Libya in Operation Odyssey Dawn, as did the UK's nuclear attack submarine HMS Triumph. Recently, Russian submarines in the eastern Mediterranean have launched cruise missile strikes against alleged terrorist targets in Syria, the latest in September.

The USS Michigan would be essential in any strike against against North Korea. Tomahawk missiles, flying low and slow to avoid radar can be expended on well-defended targets without the risk of losing a pilot. Tomahawks would be used to strike known headquarters, air defense radars, missile sites, and airfields, suppressing Pyongyang's air defenses.