Has North Korea declared war on South Korea? This is the question many have been left wondering, ever since North Korea’s  leader, Kim Jong Un declared last month that South Korea is its “principal enemy”.Kim may be an erratic and paranoid leader, who has pushed much of his country to starvation with his isolationist policies.But this change was historic, marking the abandonment of a policy, held for more than 50 years, that the countries were aiming for peaceful reunification.Today, North Asia correspondent Eryk Bagshaw and explainer reporter Jackson Graham on what has prompted this stark change of events. And whether a Donald Trump presidency could prompt Kim to escalate things even further.Subscribe to The Age & SMH: https://subscribe.smh.com.au/See omnystudio.com/listener for privacy information.