Gaius Cassius Longinus ( ; October 3 , before 85 BC – October 3 , 42 BC ) , often referred to as Cassius , was a Roman senator and general best known as a leading instigator of the plot to assassinate Julius Caesar . He was also the brother-in-law of Marcus Junius Brutus , another leader of the conspiracy . He commanded troops with Brutus during the Battle of Philippi against the combined forces of Mark Antony and Octavian , Caesar 's former supporters , and committed suicide after being defeated by Mark Antony
assassinate
Assassination of Julius Caesar
Gaius Cassius Longinus