Maximilian's Empire was never in control of the entire country and was in constant battle with Republican forces led by the ousted president Benito Juárez. Juárez eventually set up a government in exile in Chihuahua. Parts of the country not in control of the regency would not use stamps bearing Maximilian's image and issued a few provisional stamps. More commonly those areas reverted to using pre-stamp postal markings with "franco" stamps. These stampless covers issued after the advent of adhesive stamps are known to philatelists of Mexico as "Sellos Negro", or "Black (hand)stamps".