Hough their horses - i. e. cut the sinews of the hinder hoofs. This sinew once severed cannot be healed, and the horses would thus be irreparably lamed. This is the first appearance of horses in the wars with the Canaanites (Deuteronomy 17:16 and note).
Related Commentaries of Joshua 11:6
Joshua 11:6
6 And the LORD said unto Joshua, Be not afraid because of them: for to morrow about this time will I deliver them up all slain before Israel: thou shalt hough their horses, and burn their chariots with fire.