Whom did Julius Caesar defeat to gain control of the Roman Senate?

Julius Caesar gained control of the Roman Senate primarily through his military and political struggles against Pompey. Pompey was a significant rival and a member of the First Triumvirate, alongside Caesar and Crassus. The conflict escalated into a civil war when Caesar crossed the Rubicon River in 49 BCE, which was a direct challenge to Pompey's authority and the Senate's decision-making. The subsequent battles led to Pompey's defeat and his eventual death in Egypt in 48 BCE, allowing Caesar to consolidate power and influence over the Senate. This victory was pivotal in Caesar's rise to dictatorial power, enabling him to implement reforms and centralize authority in Rome.