Answer:
Sulla and Marius were both powerful military and political leaders during the Roman Republic. Sulla served under Marius in the Numidian (or Jugurthine) War. They then went on to become rivals, at one point Sulla marched on Rome causing Marius to flee.
They had very different views on what was best for Rome - for example, Sulla increased the power of the Senate, and Marius decreased it.