“their…their…their.” The Hebrew text reads in the singular, “his,” but it refers to each of God’s people who were oppressed together, so we, like many other versions, pluralized it for clarity.
“have broken.” God broke the rod of the Assyrian, but also God will break the yoke of Israel’s oppressors in the future, but it is written about as if it had already happened to emphasize that it will happen. This is the idiom of the prophetic perfect (see commentary on Isa. 9:1).
“day of Midian.” This refers to the record in Judges 6-8 when God defeated Midian through the hand of Gideon. With only 300 men, Gideon defeated an army of 135,000 Midianites (Judges 7:7; 8:10).