Donald Trump says America must massively boost its nuclear capability until the "world comes to its senses." He made the statement on Twitter without providing any details or context. This comes hours after Russian President Vladimir Putin's call for his country to reinforce its own nuclear capabilities.

This open talk of nuclear arsenals is a departure from the stance of President Barack Obama, who called for the elimination of nuclear weapons in a speech in Prague in 2009. America has an estimated arsenal of about 7,000 nuclear warheads, second only to Russia, which has a few hundred more.