After the Napoleonic Wars, Sarsfield remained loyal to King Ferdinand VII of Spain. He and Henry O'Donnell, 1st Count of la Bisbal foiled a liberal plot in 1819. That year he was rewarded with promotion to Lieutenant General. But when the liberals took power the next year in the Trienio Liberal, he was banished to the Balearic Islands. He opposed the French intervention to restore Ferdinand, known as the Hundred Thousand Sons of Saint Louis. The 1830s found him leading the liberal army of Navarre during the First Carlist War. He was killed by mutineers at Pamplona in 1837, the same year he led his troops at the Battle of Oriamendi.