The Minister Coachman ("Taipu" 太僕), also known as the Grand Coachman, was responsible for the maintenance of imperial stables, horses, carriages and coachhouses for the emperor and his palace attendants, and for the supply of horses for the armed forces. His latter duty entailed the supervising of large breeding grounds of frontier pastures, tended by tens of thousands of government slaves. By the reign of Emperor Wu of Han (r. 141–87 BC) these contained 300,000 warhorses intended for use in campaigns against the nomadic Xiongnu Confederation. Some of the Minister Coachman's subordinates managed stables outside the capital city. These stables housed Ferghana horses that were imported or gathered as tribute from Central Asian countries.