Quintanilla moved to southern Chile, where he joined the cavalry and was uninvolved in politics until the outbreak of the
Chilean War of Independence. When the war broke out he fought under
José Antonio Pareja as a captain. Quintanilla defeated a force led by
Luis de la Cruz on 1 July 1813. Along the
Biobío River he launch numerous raids. Quintanilla wrote in his memoirs that either side would have won during the early portion of the war of independence if they had two companies that could properly manoeuver and retain formation. No Spanish soldiers were fighting in the war at the time and the royalist forces were made up of locals. The Abascal Carabineros cavalry squadron was formed by Quintanilla in August 1814, and he led it as a lieutenant colonel. Under his leadership he led this group victory at the
Battle of Rancagua and captured
Rancagua and
Santiago. In 1817, Quintanilla fought against
José de San Martín in
Chacabuco Province, but was unable to defeat him. All communication between the
Chiloé Archipelago and the mainland was interrupted after the
Battle of Chacabuco. At the end of the year Quintanilla arrived and took command of Chiloé. He organised a militia with 400 rifles. Contact with the mainland was not restarted until November 1821, and by that time the Spanish forces had been defeated. ==Governor of Chiloé==