Refers to damage or harm caused by war, including physical destruction, casualties, and economic loss.
It took many years for that country to recover from the war damage.
戦争被害 is a plain, neutral term for damage caused by war, while 戦禍 is a more emotionally charged, literary word for the same thing.
Compound of 戦争 (sensō, 'war') and 被害 (higai, 'damage').