With so many sources of money, Villa expanded and modernized his forces, purchasing draft animals, cavalry horses, arms, ammunition, mobile hospital facilities (railroad cars and horse ambulances staffed with Mexican and foreign volunteer doctors, known as Servicio sanitario), and other supplies, and rebuilt the railroad south of Chihuahua City.
Disgusted but having no practical alternative, Villa complied with Carranza's order and captured the less important city of Saltillo,[REF] and then offered his resignation [REF].