NORTH Korea better be watching its back today as thousands of US troops and 230 warplanes descend on Kim Jong-un’s doorstep. Vigilant Ace – a massive joint war games – kicks off today as the US and South Korea rehearse for battle with Pyongyang. Hundreds of aircraft and thousands of soldiers and airmen are taking part in the drill, which is one of the biggest ever of its kind. US and South Korean forces will be rehearsing for a full-scale war with North Korea. Nuclear fears have reignited as Kim fired his latest missile last week – his biggest and...