After fleeing Rome following Caesar's funeral, Brutus and Cassius raised legions in which part of the Roman world, setting up the eventual confrontation at Philippi?

Explication

Brutus and Cassius gathered military support in the eastern provinces, such as Macedonia, Syria, and Asia Minor, which is why the decisive battle against them was fought at Philippi in Macedonia. They did not build their base in the western provinces, Africa alone was not their staging ground, and Egypt was later the refuge of Antony and Cleopatra, not of the assassins.