Judges 12:6 ASV

Judges not only records successive waves of external oppression that God allows to come upon Israel because of their unfaithfulness to Him, it also demonstrates the effect of their corruption on their internal unity.
1. Aram oppresses; Othniel delivers. No record of internal dissent.
2. Moab oppresses; Ehud delivers. No record of internal conflct.
3. Canaan oppresses; Barak delivers. Deborah's song points out several tribes who did not answer the call to arms with Barak, but no fighting ensues.
4. Midian oppresses; Gideon delivers. Two cities refuse to aid Gideon as he pursues his victory, and he returns to bring vengeance on them. He also argues with Ephraim at the tribal level, but is able to speak to them and mollify their anger. (At this point we get the first storyline completely separate from oppression/deliverance: Abimelech, Gideon's illegitimate son, who kills his brother, and creates a city-level civil war against him.)
5. Ammon oppresses; Jepthah delivers. Ephraim has the same conflict with Jepthah and the Giliadites that they had with Gideon, but Jepthah is not able to resolve it peacefully; we see the first inter-tribal war (Although Ephraim and Giliad, which is part of Mannasah, are actually two halves of one greater tribe, the descendants of Joseph). 42,000 Ephraimites are killed.
6. Philistines oppress; Samson begins to deliver. Samson himself doesn't come into conflict with other tribes (he dies tragically in his act of deliverance). However, immediately following his story is the incident in Gibeah with the Levite's concubine that results in full scale, inter-tribal civil war. The entire tribe of Benjamin is nearly wiped out.

It is onto this stage of not only repeated external oppression, but also ever-widening internal division that the age of kings enters.