Great success in foreign affairs was accompanied by intensification of conflict in Rome itself. The main reason were limits in access to offices that affected members of the ruling class. Two processes caused serious changes in working of electoral mechanisms and political manners.
The first process was gradual impoverishment of Italian peasants. War campaigns lasting for years not only kept people away from working on their fields but also caused huge devastation of southern Italy. At the same time people who were lucky enough to make a fortune on the birth of the Empire, purchased land that was the only stable investment.
In the long run it meant concentration of landed property in big farms run by slaves whose price dropped a lot as a result of conquests. Small farmers, deprived of means of living were going to Rome where they tried to make ends meet. They were citizens only officially because in fact they were proletarians. Being citizens they still had the right to vote. For the rich and politically ambitious they were just crowd that could be bought or bullied. The way to luxurious offices led through the Assembly of Citizens, that is why political mechanisms of the late Republic showed the importance of wealth more and more clearly. It had repercussions all over Italy. Since votes got their price, proletarian citizens started to defend their votes trying to oppose to expanding citizen's rights to other inhabitants, even to allies giving military support to them.
The second process concerned changes in the Roman army. The army became regular. After the Punic wars it was impossible to conduct wars with people who were soldiers and farmers at the same time. Military service was always a large burden and became more and more unpopular. War campaigns were conducted in more and more distant places, garrisons that had to guard conquered provinces did not come home for years and even Rome started to suffer from the lack of people.
That fact was officially acknowledged in 107 BC when consul Gaius Marius gave up conscription and introduced voluntary army recruitment. Marius' reform solved staff problems of the army because the number of the poor willing to fight covered the demand for new soldiers. Initially military service was reserved for citizens but, at last, the situation changed and Roman citizenship could be received in the army.
As a result the army became an important political power, being at the disposal of people like Marius who conducted wars in provinces of the Empire. Marius was the author of one more precedent: soldiers took an oath of loyalty to the commander and not to the state.
Small farms were gradually replaced by huge latifundia, bought for booty and the gap between the rich and the poor increased. At the same time victorious leaders had new opportunities of political career. Both things turned out to be fatal for the Republic. In the end of the 2nd century BC brothers Gracchus, tribunes of the people tried to solve social problems by introducing agricultural reform that limited the power of the Senate and increased the participation of equities in rule.
The Gracchus tried to distribute resources of the Empire to broader masses of people but the only result was that they were both killed by their adversaries. The Gracchus' death meant a more aggressive political struggle; in the last century of the existence of the Republic political splits were as strong as never before, not only career but also life of the engaged politicians were at stake. It also was the time of the beginning of the so-called Roman Revolution. Political rules of Rome had been broken when the older of the brothers, Tiberius Gracchus brought about the removal of the tribune of the people, Marcus Octavianus, who vetoed his project of agricultural reform. In that way he violated a traditional rule that gave the plebeian tribunes the right to veto.
Wars conducted by next rulers made the Empire plunge into chaos. Gaius Marius led a couple of wars with conquered nations during his rule. Military conflicts became more severe during his rule, also with Roman allies who tried to get new rights for themselves.
Roman wars in Asia created a new victorious leader who had political ambitions – Sulla. After Marius's death in 86 BC Rome was left without a consul. In 82 BC Sulla came back to the capital and was appointed dictator. His first political decisions were: limiting rights of tribunes and restoration of the omnipotence of the Senate. In 70 BC Pompey became consul. During his rule chaos and corruption of the ruling class in the capital increased. Fear of dictatorship became bigger and was additionally fomented by oligarchy. However Pompey was engrossed in wars and was not interested in dictatorship.
In 59 BC Julius Caesar became consul. During his rule the Empire made as many conquests as never before. When his adversaries wanted him to go to court and clear himself of charges, Caesar made a decision that it was the end of the Roman Empire. He crossed Rubicon and started the march to Rome. That was treason although he affirmed that he wanted to defend the Empire against its enemies. Next years of his rule were filled mostly with conquests. He was killed by assassins 15th of March 44 BC.
The Republic was dying. It had got its mortal blows long before Caesar crossed Rubicon and its constitutional institutions lost their vitality and could not be restored. However the myth of the Republic, its ideology and forms had been preserved. Romans could not put an end to the old tradition. When they did it at last, they did not resemble their ancestors from the times of the Republic in any way.
More on the fall of the Roman Empire in 476, and how its downfall parallels politics in the US now: www.roman-empire-america-now.com