Which words and phrases show that the passage is a reliable source? sparta was one of the most influential city-states of ancient greece. it had the most powerful army in all of greece. warfare was the cornerstone of the spartan economy. young boys from the age of 7 were sent off to military schools to train. according to a website maintained by the history department at oxford university, sparta’s government was a monarchy ruled by two kings. leonidas was one of the most influential rulers of sparta. the british museum states that leonidas defeated the persians with only a small army. a blog maintained by a history student says leonidas fought the massive persian armies with merely 300 soldiers.