Marcus Junius Brutus was a proud, honorable Roman Senator and army commander who was perhaps most well-known for assassinating Julius Caesar.

Brutus was born in 85 B.C. He shared the name of his father, and both were descended from Lucius Junius Brutus, who was instrumental in overthrowing the last king of Rome, Tarquinius Superbus, and was one of Rome's first two consuls, in 509 B.C. The elder Marcus Junius Brutus fell afoul of the power-seeking Sulla and then allied himself with Marcus Lepidus during the disintegration of the Second Triumvirate, dying at the hands of Pompey in 77. He had married Servilia, and she was the mother of the younger Marcus Brutus.

He was just 8 when his father died. He eventually found legitimacy when an uncle, Quintus Servilius Caepio, adopted the boy in 59 B.C. Brutus found work assisting the famous statesman Cato and then worked his way up the cursus honorum, the ladder of political positions, starting in 54 B.C. with an appointment as triumvir monetalis, a person who oversaw the minting of coins for the Republic. The following year, he was quaestor. About this same time, he married Claudia, daughter of then-Consul Appius Claudius Pilcher.

Brutus was very much a fan of those who opposed tyranny and considered his father a role model. The younger Brutus opposed the great general and statesman Pompey when he acted as sole consul (head of government) in 52. In this opposition, Brutus found an ally in Caesar, who had earlier shared power in the First Triumvirate but by then had become rivals. Also at this time, Brutus won election as a pontifex, a member of a public council of priests.

Even though Brutus had opposed Pompey's sole reign, he chose to side with that general in the civil war with Caesar. Despite that stance, he found favor with Caesar after the latter's victory over Pompey, in 48 B.C. In fact, the very next year, Caesar appointed Brutus governor for the very large province of Cisalpine Gaul. Four years later, he achieved his highest rank, that of praetor, an army commander or an elected magistrate who had specific duties, most notably the administration of justice.

In the face of what many saw as increasingly tyrannical behavior by Caesar, Brutus, who had a history of opposing such acts, joined Cassius and others in planning Caesar's downfall. They decided that he would not stop in his determination to rule Rome single-handedly, and many firmly believed that, despite his public protestations, he coveted becoming king. Brutus was one of the nearly two dozen Senators who stabbed Caesar to death (ironically, just in front of a statue of Pompey) on March 15, 44 B.C. Many sources say that Caesar cried out to Brutus as he was dying (or, in some cases, while the attack was progressing). Some Senators had wanted to dispose of Caesar's trusted lieutenant Marc Antony as well, but Brutus wouldn't hear of it and convinced his fellow conspirators not to do it.

The shocking nature of Caesar's death struck a chord with a great many in Rome. Caesar was popular with the common people and had friends in high places as well. What Brutus had intended as a delivery from tyranny instead appeared to many as a violent shift in power. Despite the conspirators' very public pronouncements of their intentions and their frantic efforts to rebuild trust in the ideas of the Republic, Brutus and Cassius and the others found themselves outcasts. The arrival of Octavian, Caesar's adopted nephew, coupled with a rousing funeral speech given by Antony, cemented the tide against the conspirators.

Brutus fled Rome, ending up in Greece, where he found sympathizers. He had also brought his army with him. Octavian, marching at the head of an army, convinced the Senate to elect him consul and then proclaimed a new statute that outlawed the murder of a dictator. Brutus, Cassius, and their fellow conspirators were thus guilty, even though the law was not in place when they had acted.

Cassius had fled to Syria, also with his army. He and Brutus joined forces in Asia Minor and campaigned against Roman forces there. Antony and Octavian joined forces, gathered a large armed force, and set sail for the east, to do battle with Brutus and Cassius. The result was the Battle of Philippi, in 42 B.C. In that struggle, Brutus's forces put Octavian's to flight; however, Antony forced Cassius's forces to leave the field of battle. An embarrassed Cassius took his own life, and Brutus took over his army. A subsequent clash in the same general area resulted in a full defeat for Brutus, who fled into the surrounding countryside and then took his own life, rather than be captured and taken back to Rome. He was 43.

Two years earlier, Brutus had divorced his wife, Claudia, and then quickly married again, to his cousin Porcia, whose father was Cato. With neither wife did Brutus have children.