noun, noun or participle which takes 'suru', intransitive verb
surrender; fall (of a castle/position)
Rare, literary term for a fortress or position being surrendered or falling to an enemy. In modern Japanese, 陥落 or 降伏 are far more common.
城が敵の猛攻の前に失陥した。
The castle fell before the enemy's fierce attack.
歴史
The history book records, 'The castle finally surrendered.'