Final answer:
Sargon conquered Sumer with a large and disciplined standing army, supported by strong administrative practices and the appointment of governors for controlling conquered territories.
Step-by-step explanation:
Sargon was able to conquer Sumer primarily because he had a large and disciplined army, which was the world's first standing army. His military success was also supported by his innovative administrative techniques, such as appointing governors to manage the conquered cities and developing an effective system of tributes to sustain the empire.
Sargon's rise to power and subsequent conquests laid the groundwork for future Mesopotamian empires, demonstrating the effectiveness of a strong, centralized military and administrative state.