Though Sulla won a decisive victory at the Battle of the Colline Gate, it was a very close-run thing. Sulla came very close to losing, and only the unexpected success of Marcus Licinius Crassus turned the tide in his favor.
What if Crassus had failed, or even been killed, causing Sulla to lose the battle?
What if Crassus had failed, or even been killed, causing Sulla to lose the battle?