Judges 10:9

Moreover, the children of Ammon passed over Jordan
Not content with the oppression of the tribes on the other side Jordan, which had continued eighteen years, they came over Jordan into the land of Canaan to ravage that, and bring other of the tribes into subjection to them, particularly the three next mentioned, which lay readiest for them, when they were come over Jordan:

to fight also against Judah, and against Benjamin, and against the
house of Ephraim
who lay to the south and the southeast of the land of Canaan, and were the first the Ammonites had to fight with and subdue, when they had crossed Jordan to the east of it:

so that Israel was sore distressed;
by the Ammonites in the east, threatening those three tribes, mentioned, and the Philistines on the west, who gave disturbance to the tribes that lay nearest them, as Asher, Zebulun, Naphtali, Issachar, and Dan; and this distress was begun the same year in different parts, by different enemies.