Roman imperium, or the power of law and command, was fully concentrated in the patrician class. The consuls were elected from among the patricians, as were the quaestors, praetors and censors. The ensuing class conflicts from the domination of political power by one class over another, in a virtual transfer of power from King to Senate, was called "the struggle of the orders". In effect, it was simply the recurring pattern of the patrician class attempting to hold onto power, while the plebeians worked to rise to social and political equality. The patricians, while mostly secure in their wealth and noble foundation, were also unable to exist without the plebeians. The Plebeian class not only produced the grain and supplied the labor that maintained the Roman economy; they also formed the recruiting basis as soldiers for the Legions.
In 494 BC, only 15 years after the founding of the Republic, a secession of plebeians to the Sacred Mount outside Rome, ushered in a fundamental change to the Republican government. The Plebes formed a tribal assembly, and their own alternative government, until the patricians agreed to the establishment of an office that would have sacrosanctity (sacrosanctitas). This was the right to be legally protected from any physical harm, and the right of help (ius auxiliandi), meaning the legal ability to rescue any plebeian from the hands of a patrician magistrate. These magistrate positions were labelled as Tribunes or tribuni plebes. Later, the tribunes acquired a far more formidable, and often manipulated power, the right of intercession (ius intercessio). This was the right to veto any act or proposal of any magistrate, including another tribune, for the good of the people. The tribune also had the power to exercise capital punishment against any person who interfered in the performance of his duties. The tribune's power to act was enforced by a pledge of the plebeians to kill any person who harmed a tribune during his term of office.
In 451 BC, another Plebeian secession led to the appointment of the decemvirate, or a commission of ten men. This eventually resulted in the adoption of the bronze engraved Laws of the Twelve Tables, and raised the number of Plebeian Tribunes to 10. In 445 BC, the Canuleian law legalized marriages between patricians and members of the plebs. Along with later inter-class adoptions, plebeians were allowed additional class mobility and eventual inclusion into previous Patrician only magistracies. In 367 the plebeians gained the right to be elected consul, and in 366 the first was elected. Thereafter, the Licinian-Sextian laws demanded that at least one consul be a plebeian. After the completion of the term of consular office, the plebeian consul became a member of the Senate resulting in the disintegration of the patrician hold on the Senate. Furthermore,in 300 BC, plebeians were allowed to serve at all levels of the priesthood, thus making them religiously equal to the patricians. Finally, the greatest achievement of power for the people, in 287 BC, the decisions and legislation of the plebeian assembly, Concilium Plebis or "Council of the Plebeians", became not only binding on the plebeians, but on the entire Roman citizenry.
All power was not shifted away from the patricians, however. While still maintaining significant power through clients and the prestige of their heritage, they were also able to turn the tables. Using the plebeian adoption methodology for upward mobility, some patricians used it to adopt into the plebeian class and become available to serve as plebeian only Tribunes. While a rare occurrence, such mobility made made the entire political spectrum open to the ruling classes.
This political upheaval brought about a new aristocracy, composed of patrician and wealthy plebeian families, and admission to the Senate became almost the hereditary privilege of these families. The Senate, which in original function maintained no law making, and little administrative power, became a powerful governing force. They oversaw matters of war and peace, foreign alliances, the founding of colonies, and the handling of the state finances. The rise of this new nobilitas ended the conflict between the upper echelons of the two orders, but the position of the poorer plebeian families was not improved. In fact, a class designation of equestrian (knight), originally composed of patrician senatorial families, developed into one including plebes that signified a particular level of wealth, and further separated the plebeian elite from the common people. The decided contrast between the conditions of the rich and the poor led to struggles in the later Republic between the aristocratic party and the popular party. These struggles developed into one of several major factors in the eventual collapse of the Republican system.