Peru

In 1820, Gana entered the service again in Peru, under the orders of General José de San Martín. Gana with his battalion captured the City of Huaras with the whole garrison, and, as a consequence, the provinces of Trujillo, Lambayeque, and Piura pronounced for the insurrection, leading to the whole northern portion of Peru being wrestled from the rule of the viceroy. The viceroy, José de La Serna, was forced to evacuate his capital, Lima, on July 6, and on the 12th San Martin occupied the city. Independence was solemnly proclaimed on July 28.

Meanwhile, Gana took part in the assault of Callao, on August 14, and after the final surrender of September 21, he was promoted to major. Gana participated in General Sucre's expedition to the south, and commanded a column that attacked the Spanish forces at Quilca (August 14, 1823), and, notwithstanding the loss of one third of his troops, routed the enemy and pursued him toward Arequipa.

Chile

Ganas's tomb in the Cementerio General de Santiago

In October 1823, Gana returned to Chile, and in 1825 was sent with his battalion under Colonel Sanchez to garrison the city of Talca against the attacks of the bands of the Pincheira brothers, whom he surprised and defeated. In December of the same year he was promoted to colonel, and his battalion formed part of General Ramón Freire's expedition to Chiloé, which archipelago was still held by the Spanish under General Antonio Quintanilla. He participated in the decisive Battle of Bellavista (January 14, 1826), and was commissioned by Freire to sign the capitulation of Pudeto on January 19 which surrendered the rest of Chilean territory to the independentist forces. During the Chilean Civil War of 1829, he joined the liberal forces under General Ramón Freire, and, after their defeat at the Battle of Lircay (April 17, 1830) declined to serve under the government of the conservatives, and retired from active service.