American WWII bomb explodes at Japanese airport, causing large crater in taxiway

It was originally a military airfield during the war, which explains why there are bombs in the ground.

Eh, at my local train station in a bigger city in Austria they still find American and English bombs every year. Whenever something is dug up for repairs or to expand the train station or for whichever other reason, a bomb specialist is examining the area first, when they find a bomb they either safely remove it to detonate it somewhere else, or if its too unstable (roughly every five years if my memory serves me right) we get radio broadcasts warning us when it will be detonated so we can prepare (close all windows, sometimes those living near it have to leave their houses).

That train station wasn't involved with the military (apart from soldiers using trains for transport, but by that logic you can bomb anything because soldiers use houses for sleeping and hospitals for medical treatment etc.), but sadly both Germany and the UK tried to destroy as much as possible in the other country.