Short answers, pulled from the story.
Polybius observed that the Roman Republic distributed power among three distinct groups: the Senate, the Consuls, and the Assemblies. He described this arrangement as a mixed government that prevented any one person or group from seizing total control. This ancient observation laid the groundwork for understanding how power could be divided to preserve freedom.
John Locke introduced a distinction between three types of state power: legislative, executive, and federative. He defined legislative power as the authority to direct how the force of the commonwealth should be employed, while executive power involved the actual enforcement of laws. Federative power dealt with foreign affairs, including war, peace, and alliances.
Charles de Secondat, Baron de Montesquieu published The Spirit of Law in 1748, where he articulated a system that would become the cornerstone of modern constitutional design. He described the distribution of power among a legislature, an executive, and a judiciary. Montesquieu argued that each branch must have its own source of legitimacy and function to prevent any one from usurping the others.
The United States Constitution of 1787 embedded the principle of checks and balances into the structure of government. Alexander Hamilton redefined the judiciary as a distinct branch in Federalist No. 78, and James Madison argued in Federalist No. 51 that ambition must counteract ambition. This system ensured that each branch had the constitutional means to defend its own powers.
Bolivia, Costa Rica, Panama, Nicaragua, and Venezuela include an electoral branch to oversee elections. Taiwan's Control Yuan serves as an auditing branch, tasked with monitoring government performance and impeaching officials for misconduct. The Republic of China implemented a five-branch system that included the Executive Yuan, Legislative Yuan, Judicial Yuan, Control Yuan, and Examination Yuan.