Iraq had no connection to 9/11 and no WMDs. It did have a brutal dictator and lots of oil. Therefore we invaded the country and set off wars that engulfed the region and led to the formation of ISIS, just as the war against the Soviet Union in Afghanistan led to the formation of al-Qaeda. When will we ever learn?
Now the pro-war wing of the GOP is touting the danger from North Korea, a poor nation with a large army that is a threat only to South Korea and perhaps China. China can defend itself and perhaps South Korea can too. The difference is that North and South Korea want to reunite. Let them work out their differences themselves.
Japan and the Koreans do not get along. If the development of North Korean missiles is felt to be a threat to Japan, let Japan deal with it through discussions or the purchase of anti-missile systems from the US. If US troops in South Korea and Japan are threatened in the future by North Korean missiles, withdraw US troops from the area.