Ambush
noun
A soldier only lays herself down when she's about to ambush the enemy! If you see some soldiers laying around, it's not that they're lazy, it's because they're getting ready to pounce!
ふくへい
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
伏兵に襲われたんだ。
They were attacked by an ambush.