structural:expansion, structural:summarization
Hegemony of Jin (636–628)

When Duke Wen of Jin came to power in 636 after extensive peregrinations in exile, he capitalized on the reforms of his father, Duke Xian (r. 676–651), who had centralized the state, killed off relatives who might threaten his authority, conquered sixteen smaller states, and even absorbed some Rong and Di peoples to make Jin much more powerful than it had been previously. When he assisted King Xiang in a succession struggle in 635, the king awarded Jin with strategically valuable territory near Chengzhou.

Duke Wen then used his growing power to coordinate a military response with Qi, Qin, and Song against Chu, which had begun encroaching northward after the death of Duke Huán of Qi. With a decisive Chu loss at the Battle of Chengpu in 632, Duke Wen's loyalty to the Zhou king was rewarded at an interstate conference when King Xīang awarded him the title of bà.

After the death of Duke Wen in 628, a growing tension manifested in interstate violence that turned smaller states, particularly those at the border between Jin and Chu, into sites of constant warfare; Qi and Qin also engaged in numerous interstate skirmishes with Jin or its allies to boost their own power.