Over 2,000 years ago, the Greek historian Herodotus wrote about a dazzling group of elite soldiers. These impressive troops had one important job: to protect the powerful Persian king. Dressed in gold, they were unlike any soldiers Herodotus had seen before.

They would become known as the Immortals.

According to the Greek historian Xenophon, King Cyrus the Great believed that ordinary guards were not enough to protect him from everyone who might wish him harm. So Cyrus created an elite force of 10,000 lancers, or doryphoroi, recruited from lower-class Persians. These guards watched over the palace day and night whenever the king was there.

When Cyrus traveled, these guards accompanied him, marching in carefully ordered formation on either side. They also guarded the royal tent during military campaigns and expeditions.

Herodotus described 10,000 specially selected Persian soldiers. One thousand of these men carried spears decorated with golden pomegranates, while the remaining 9,000 carried silver ones. The most fascinating part: there were always exactly 10,000 of these troops. If a soldier died or fell ill, another immediately replaced him. This is how they became known as the Immortals.

According to Herodotus, the Immortals were the most richly dressed troops in the Persian army. They glittered with gold ornaments and were accompanied by carriages carrying women, servants, and special provisions, all transported on camels and mules.

Another description of the Persian army comes from the ancient Greek writer Heraclides. He described a special group of soldiers within the Immortals called the mēlophoroi, which translates to “apple-bearers.” They earned this name because of the apple-shaped decorations at the bottom of their spears.

This smaller group of exactly 1,000 men served as the king’s closest personal bodyguards. They were all Persian by birth and were carefully selected for their appearance and noble blood. They were described as dazzling in luxury, adorned with gold and precious stones.

The 1,000 men never left the king’s side, whether he was at the palace or on the battlefield. At the Battle of Gaugamela, they fought beside King Darius III and surrounded him during the retreat. During ceremonial processions, they marched directly behind the royal chariot. According to a Roman historian, they were even in charge of caring for the king’s robes, and a section of the palace was reserved specifically for them.

Adorned in gold, the Immortals were quite a sight to behold. Fearsome and loyal, they would become legendary in the ancient world. For the Persian king, having the soldiers by his side meant the difference between life and death.