Russia has successfully tested a nuclear-capable, nuclear-powered underwater drone, President Vladimir Putin said Wednesday, defying US President Donald Trump's warnings with Moscow's second test of a new nuclear weapons system in just a few days. Putin on Sunday oversaw a test of another advanced nuclear-capable weapon -- the Burevestnik cruise missile, which he said had an "unlimited range". Trump called that exercise not "appropriate". "Yesterday, another test was conducted for another prospective system -- the unmanned underwater device 'Poseidon,' also equipped with a nuclear power unit," Putin said in televised remarks while visiting a military hospital treating Russian soldiers wounded...