The Roman Republic and the Roman Empire grouped their soldiers into organized military units. This military unit was called a A. phalanx. B. horde. C. legion. D. squadron.

C. Legion is the correct answer.

Explanation:

In Ancient Rome the military was a highly organized institution with a clear cut system of rank and number of different divisions of the basic unit, the legion. The legions were numbered and each legion had 5500 men. It was further divided into six centuries of 80 men each. the century was commanded by Centurian and each century had a tesserarius, a signifier, a cornicen, and an optio. Legion also had 120 cavalrymen who were used as scouts.

The Roman Republic and the Roman Empire grouped their soldiers into organized military units called a:

C. legion.