Albert Barnes Commentary Judges 5:8

"They chose new gods; Then was war in the gates: Was there a shield or spear seen Among forty thousand in Israel?" — Judges 5:8 (ASV)

The “war in the gates” describes the hostile attacks of the Canaanites, which were the punishment of the idolatry of the Israelites (compare the marginal references), and the reduction of Israel to an unarmed and unresisting state under the Philistine dominion. See Judges 3:31 note.