Nuclear submarines are some of the most impressive and technologically advanced warships of all time, and the United States Navy has a boatload of them. In fact, every submarine operated by the U.S.

The Trump administration has repeatedly said the U.S. should be in control of Greenland, which is part of Denmark and NATO.

The death of the last treaty between Russia and the U.S. that limited the size of nuclear arsenals may spark a new arms race, says a former security council director.