A new defense initiative aimed at intercepting missiles before they can hit the U.S. has been announced, but how will this Golden Dome work?

The president would need to rely on Ottawa to track Chinese and Russian missiles that could come at the U.S. from over the horizon.

It would be the equivalent of us going back 1,000 years and having to start from scratch." In response to these hypothetical - but experts say quite possible - threats, US President Donald Trump has set his eyes on a "next generation" missile shield: the Golden Dome.