Charles Ellicott Commentary Judges 10:9

"And the children of Ammon passed over the Jordan to fight also against Judah, and against Benjamin, and against the house of Ephraim; so that Israel was sore distressed." — Judges 10:9 (ASV)

Moreover. —Rather, and. Eighteen years’ oppression of the Trans-jordanic tribes emboldened them to attack the others.

Was sore distressed. —The same expression is used in Judges 2:19.