The Korean peninsula has been home to one of the most violent and confusing states on the planet for some time. North Korea formed in 1948, enjoyed a whopping two years of military buildup, courtesy of the USSR, before launching into its first war, the Korean War. During the Korean War, the United States made several mistakes that ultimately culminated in the stabilization of North Korea and its rogue state status. In support of South Korea, the United States entered the war with some manner of success, pushing North Korean soldiers from the southern tip of the Korean peninsula past the original boundary between North and South Korea. The United States had succeeded, but as is so often the case with the United States, it was not enough. US forces aggressively pursued the North Korean army north almost to the Chinese border. China mistook our overzealous attack on Northern forces as a potential threat and entered the war, gaining North Korea a powerful ally that has been less than willing to control North Korea's antics.
Since the end of the Korean war by armistice in 1953, which only suspended the fighting and established a demilitarized zone between the two states, North Korea has aggressively pursued the development of all manner of military weapons, committed all types of atrocities on its populace and pursued antagonistic international agenda's completely unfettered by international law and international scrutiny. Their aggression has created a never-ending state of tension between the two Korean states that could lead to war at any moment. The Korean Peninsula may seem far away from the United States however, US troops are regularly rotated out of the region. According to Reuters, South Korea and the US participated in the largest joint training exercise ever between the two states March 7, 2016 involving 15,000 US troops and approximately 300,000 South Korean troops.
In fact, the threat of war has been North Korea's chief weapon for decades. In the hopes of gaining food aid from the international community, North Korea engages in a tactic called saber rattling. How it works is the North Koreans step up some type of violence in the region, the international community steps in to avoid an all out war. In exchange for food aid, North Korea de-escalates the conflict it began. For example, according to the BBC in 2010 the North Koreans shelled a small South Korean island resulting in several months of high tensions. In the end, the international community funded food aid programs in 2011 which deescalated the conflict. Unfortunately, this had the unintended consequence of allowing North Korea to free up resources that would otherwise be spent on food for weapons. What little estimates can be made about the country, its populace is extremely poor and starving. US based food aid programs to North Korea have slowly lost funding by donors because of the lack of progress in North Korea and the US economic recession. What little is left may not be enough to deter the North Koreans.
Saber rattling is a tried and true tactic for the North Koreans however, tensions have been growing over the new leader of North Korea, Kim Jong-un. The previous leader understood that saber rattling was simply for show, the international community has yet to see if Kim Jong-un will commit to active military engagement. Where the previous leader Kim Jong-il blustered and bluffed, Kim Jong-un has continued to make greater and more pressing threats unsettling the international community. The North Korean military has been put on stand by, US satellites detected potential rockets being moved towards the border of the country, and Kim Jong-un has announced the country tested a hydrogen bomb and would use it if they felt threatened. If the situation continues as is, conflict is unavoidable and the United States will invariably be drawn into another international conflict.