US Secretary of Defence Jim Mattis warned today that North Korea would face a massive military response if Pyongyang ever used its nuclear weapons. He said at a press conference on his trip to Seoul that any attack on the United States or their allies will be defeated and use of nuclear weapons will be met with a massive military response. <br/><br/>Tensions have been running high on the Korean peninsula, with the North conducting its sixth nuclear test last month and test-launching multiple missiles capable of reaching the US mainland.