Decline And Fall of the Roman Republic
Part I: Here Comes The New Boss
The conflict began almost as soon as the last Roman king was kicked out in 509 B.C. The patricians controlled the Senate, and the plebeians served as soldiers in Rome's armies. During wartime, plebeian farms had no one to run them, and patricians would provide loans to pleb families to keep them running. However, these loans often came with usurous interest, and if a family could not repay, it was within the patricians' rights to seize the farm, and carry the family away into slavery. Many plebs were impoverished, beaten, enslaved and even murdered by their wealthy creditors.
In 494 B.C., Under these conditions, the plebs revolted, and refused to fight Rome's wars. The patricians ultimately allowed the plebs into the Senate as tribunes, offices created to protect the interests of the plebs, and order was restored.
Each time there was a conflict, the plebeians mutinied or threatened to do so until the Senate acquiesced. This resulted in significant changes to Roman law, such as the Lex Licinia Sextia in 367 B.C., which opened all state and senatorial offices to the plebs. (It still didn't abolish enslavement for debt, though - that didn't happen for another 40 years.)
The Conflict of the Orders finally ended in 287 B.C. with the Lex Hortensia, removing the last patrician check on plebeian power and giving them full political equality.