A challenge for war? This is a challenge worth accepting. After all, we can't give up without at least giving it a try or making some kind of an attempt.

Note that 挑戦 refers to a challenge not in the sense of a difficult, challenging task, but in the sense of a bold or daring attempt to take on that task — whether that's defeating a formidable foe, performing an impressive feat, or tackling a tricky problem.

This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.