government. This officer is appointed by the president. He is required to perform and execute such duties as shall, from time to time, be enjoined on or entrusted to him by the president, agreeably to the constitution, relative to military commissions or to the land forces, or warlike stores of the United States, or to such other matters respecting military affairs as the president shall assign to the department of war, or relative to granting of lands to persons entitled thereto for military services rendered to the United States, or relative to Indian affairs.