Why were the Persian Immortals called the Immortals?

The Immortals served as an Imperial Guard and a standing army during the Persian Empire's expansion and the Greco-Persian Wars. They were so named because the group always contained exactly 10,000 men, as each man who retired, was killed, wounded, or seriously ill would be immediately replaced by a reserve.

Explanation:

these the citzens and goverment come to terms some of the amendments gave the states more power then the goverment and some protocted americans rights