What is "ichirgu-boil"

The Ichirgu- boila or Chargobilya ( Old Bulgarian , ) was a high-ranking official in the First Bulgarian Empire. He was the commander of the garrison of the capital and was the third most important person in the state after the ruler and the Kavkhan. In peace-time the ichirgu-boila had diplomatic functions. According to some data the ichirgu-boila personally commanded a squad of 400 heavy cavalrymen.