Which allies? North Korea will not invade South Korea anytime soon. They are more than aware that SK has a far better army, and South Korea, on the other hand, does not want a conflict with North Korea and have been criticizing the US for its militaristic approach. If NK wanted to invade SK, they would have done it again already. They literally have had artillery pointing at Seoul for decades now. It's also very very unlikely that they'd ever nuke South Korea, as their aim was to unite Korea, not destroy half of it.
That's what you get when you threaten an entire country and its people ^^