Since the North Korea conducted its third nuclear test and the new round of sanctions on it by the UN, we have seen a dramatic escalation of tensions in the Korean peninsula.
The North Korean leader signed off on papers to get its missiles ready to strike at US forces and the US mainland itself. It deliberately leaked photos of is "plans" as a show of intent. North Korea declared that its in a state of war with South Korea and abrogated the armistice that ended the Korean War in 1953.
The US and South Korea started a military exercise in which the US has sent strategic bombers B-52s,B2s and stealth fighters F22 to take part in the exercise which signals a firm resolve to stand up to the North Korean belligerence.
The young leader of North Korea seems to have taken to belligerence to strengthen his position in the country and taking an anti US stance is the only way to do that. Over the head the US has resorted to sanctions and measured response to North Korean belligerence but this time its military response seems to be a carefully thought out plan to corner the inexperienced leader of North Korea.
The North Korean leader needs an excuse to declare a "victory" in the current stand off. The US response has denied any room for the North Koreans to do that. The North Koreans have shown an intent to use nuclear weapons but the US response indicates they have good intelligence on the nuclear weapons or the lack of it of the North Koreans. The North Korean missiles do not have the capability yet of hitting targets on US mainland and they may not yet have a working deploys me warhead nor the numbers to threaten the US or South Korea. Even the South Koreans have upped the rhetoric saying they will reply in the strongest possible manner against any North Korean provocation.
I think the reason for this is to force a change in North Korea. The Kim Jong Un not having any "victory" in this round of escalation will severely dent his standing among his army and his countrymen leading to a possible instability. On the other hand, if the North Koreans do anything adventurous, it may well spell the last war on the Korean Peninsula and the North Korea ceasing to exist and united under South Korea. Either way, it looks to be a win win situation for the US and South Korea.