Final answer:
Brutus and Cassius fled Rome and became governors of the Eastern provinces, with Brutus taking Macedonia and Cassius governing Syria, where they built armies for the Battle of Philippi.
Step-by-step explanation:
After the assassination of Julius Caesar, Brutus and Cassius fled the city of Rome due to the political unrest that followed. They became governors of Eastern provinces. Brutus took control of Macedonia and later governed most of Greece, while Cassius became the governor of Syria. Both provinces were strategic and fertile, with Syria serving as an important province due to its wealth and Macedonia due to its military significance. They used these provinces as power bases to build armies in preparation for the ensuing conflicts with the Caesarian forces, leading up to the pivotal Battle of Philippi.