The Roman Republic began when the Romans, under Junius Brutus overthrew a particularly cruel Etruscan ruler, and the Roman Republic was proclaimed in 508 B.C.E. The Republic lasted for almost 500 years, with an unwritten constitution. It was probably the most stable form of government that the Roman people ever knew.
The Republic fought the Punic Wars with Carthage, and were successful; however it proved costly in the long run. Roman soldiers who fought in the war had been forced to abandon their farms to fight. As a result, when they returned from the war, their farms were in ruins and many lost everything to larger landowners. Since they had no means of supporting themselves, many Roman soldiers remained loyal to the generals under whom they had fought, including those who had fought with Julius Caesar.
The uncertainty of the times led to a bloody civil war, with one Lucius Cornelius Sulla ultimately taking control. Sulla published a "proscribed list" of his enemies to be executed. Julius Caesar was one of those enemies, but Sulla did not consider him a threat; plus he was in Greece at the time and not a serious problem.
Julius Caesar spent large sums of his own money on circuses and gladiator fights which made him popular with the common people. He, along with Pompey and Marcus Crasus formed the first Triumvirate to rule the remains of the republic. Caesar was given command of Gaul, with the understanding that he would remain there. The Rubicon, a tiny river, was the line of demarcation which he was not to cross. Crasus died fighting in Mesopotamia; and when conservatives attempted to maneuver Caesar out of the government, he relied on his popularity to march on Rome. He is said to have uttered Jacta alia est when he crossed the Rubicon. (The phrase, "cross the Rubicon" is now used when one is said to have reached the point of no return.) When he arrived in Rome, Pompey fled to Egypt hoping to ally with Ptolemy IV and Cleopatra, but was murdered there. Caesar then moved into Rome and assumed the title of Dictator, an office provided for in the Roman Constitution in the event of a national emergency. Because members of the Senate feared Caesar would convert the Republic into a kingdom with himself as king, he was assassinated in 44 B.C.E.