Born in Yapeyu, Argentina, his family took him to Spain at a young age. His military career began at age 11 in 1789, fighting with the Spanish against the French in the Revolutionary Wars. He achieved great distinction throughout the Napoleonic Wars, being decorated for his part in the Battle of Ballen, and reaching the rank of Lieutenant Colonel. During this time he became acquainted with supporters of South American independence.
Campaign for Independence
He resigned from the Spanish army in 1811 and moved to England, where his new-found sympathy for colonial independence dovetailed with a British desire to reduce Spanish influence in the Americas. He sailed to Buenos Aires on a British frigate, and a brilliant six-year campaign, including an audacious crossing of the Andes, drove royalist forces from the whole of southern South America.