The Paighan also known as Paygan were a militia light infantry unit within the Sassanid army and formed the bulk of its infantry force. The Paighan were sometimes referred to as being used as "meat shields".
The Paighan were a conscription force, recruited from the peasant population of the Sassanian Empire. According to the Chronicon Anonymum, the vast majority (120,000) of Sassanian Emperor Khosrau I Anushirvan's army of 183,000 was made up of Paighan. Despite being referred to as meat shields, the Paighan were frequently used in sieges and served as pages for their Savaran masters. These troops would generally have had the lowest morale of all troops in the Sassanian army and would cluster together for mutual protection. According to Arab historians, during the Battle of al-Qādisiyyah the Persian commander Rostam Farrokhzād refused to provide the Paighan troops with food and water the night before the battle. However, in the Arab camp all soldiers there were being provided with supplies, including the peasants. This may be the reason why many of the Paighan soldiers in the army defected to the Arab side before and after the battle.
The Paighan were lightly armed with short light wood or wickerwork shields, boiled leather cap and short spears. Some of the paighan would have however had to equip themselves with their own weapons. These tended to be agricultural equipment such as pitch forks, daggers, axes and sickles. The Paighan would have lacked decent armor, making them very vulnerable in hand to hand combat. They would have stood little chance against Roman troops. This is the reason why Sassanians developed their own heavy infantry to counter that of Rome's.
Right for you to despise them. For their whole infantry is nothing more than a crowd of pitiable peasants who come into battle for no other purpose than to dig through walls ... and in general to serve the soldiers. For this reason they have no weapons at all with which they might trouble their opponents, and they only hold before themselves those enormous shields and huge elephants.