Death In Battle, KIA
Noun and する verb
せんぼつ
たくさんの戦没した兵士たちがここに埋められています。
Many soldiers who were killed in action are buried here.
When a person dies in a war they're considered to have been killed in action. There are lots of memorials around the world for people who died this way.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.