Although the Spanish were able to impose effective control over much of the region by 1537, the conquerors soon fell to fighting among themselves over the spoils of their success. Order under the Spanish viceroys was gradually established and extended, but not without regular and persistent challenges at the local or regional level from dissident indigenous groups, often in the name of the Inca. Because of the economic importance of Peru to the crown, second only to Mexico, there was a larger Spanish military presence here than in the rest of Spain's New World empire. Even so, until the colonial reforms of 1764 by the Bourbon dynasty in Spain, the military garrisons were small and stationed in the cities. Many career officers and troops served their tours of duty in these Peruvian cities and then returned to Spain. Landowners were left to their own devices for protecting their local interests, so they raised private militias as necessary. Military forces during the last sixty years of Spanish rule were more regularized and institutionalized into three categories: Spanish regiments on temporary service, others on permanent colonial service, and colonial militias.

The independence movements that began to sweep Latin America in 1810 during Napoleon Bonaparte's occupation of Spain and his brother Joseph's brief reign were slow to reach Peru, but they inevitably arrived. New regiments raised locally to protect the viceroyalty initially defeated independence forces attempting to liberate the area from outside, but eventually played an important role in ousting the Spaniards themselves. However, the main impetus for independence came from Simón Bolívar Palacios and José de San Martín from the viceroyalties of New Granada and Río de la Plata (River Plate), respectively. It was San Martín who brought his army to Peru from Chile and took Lima after refusing to negotiate with the viceroy, declaring independence on July 28, 1821, and making himself military dictator. He used this position to advance the cause of independence and to prepare militarily for the final campaigns against the Spanish. This preparation included establishment of a series of military units, the first of which, called the Peruvian Legion, was formed on August 18, 1821. In addition, he formed Los Montoneros, a mounted guerrilla force, to harass the royalists and shield the operations of the republican regulars.

San Martín resigned and went into exile in France before full independence was secure, when he realized that he and Bolívar would not be able to cooperate. Nevertheless, San Martín's earlier organizational and training efforts earned him the sobriquet of protector of Peruvian independence and founder of the EP. As San Martín had expected, Bolívar went on to win the Battle of Junín in August 1824, with significant help from the forces that San Martín had prepared. These Peruvian units also made important contributions to the final battle for independence at Ayacucho on December 9, 1824, under the command of General Antonio José de Sucre Alcalá (see Independence15c ce Imposed From Without, 1808-24 , ch. 1).

Data as of September 1992