Kim is taking initiatives to bolster defense against hostile adversaries because he has no choice. He has repeatedly called for the US and South Korea to tamp down their aggressive military exercises to no avail — and their leaders even have the nerve to call North Korea the aggressors. As long as the US and South Korea are saber-rattling, Kim will make sure North Korea is as prepared as possible.
Kim's aggressive actions and words are pushing for war between North Korea and the US. Pyongyang has celebrated its development of a nuclear weapons program and has conducted many missile tests in close proximity to South Korea. Now Kim's military is conducting “actual war drills” while claiming he's just worried about self-defense. The US and South Korea have had to bolster their militaries just in case Kim crosses the line.