In Act 1 of Shakespeare's Julius Caesar, Caesar's recent victory over Pompey is revealed. Pompey was a respected general and long-time hero of Rome. Their battle was a civil war.
Caesar's victory has made him extremely popular with the Roman crowds, and therefore extremely powerful.
We also learn, though, that there are some Roman leaders who apparently liked Pompey better than they like Caesar. This creates immediate tension in the play. These leaders don't like the fact that Caesar is being treated as a hero for defeating a fellow Roman, rather than for defeating an actual enemy of Rome. The victory over Pompey brings Rome no wealth or slaves or hostages.