Fearing a threat to Chilean commercial and shipping interests, and even sovereignty by the newly created Peru-Bolivia Confederation led by Bolivian general Andrés de Santa Cruz y Calahumana, Chile declared war on the confederation in 1836. The Chilean Navy, gradually run down since the end of the struggle for independence, consisted of only two small vessels. Nevertheless, once more it rapidly tripled its strength by captures from the larger Peruvian fleet. Within a year, the Chilean Navy had established control of the sea.

On land, a Chilean force of approximately 2,800, under the command of Blanco Encalada, landed at Islay in southern Peru in October 1837, occupying Arequipa after a long and arduous march, during which the Chileans were decimated by disease. Following an encounter at Paucarpata with an army under the command of Santa Cruz, the Chilean force concluded a peace treaty, the Treaty of Paucarpata, on November 17, before returning to Valparaíso rather ignominiously. The Chilean government repudiated the treaty in indignation and in 1838 dispatched a better-prepared Chilean force under General Manuel Bulnes Prieto. Landing at Ancón, north of Lima, on August 6, this force commenced a slow march southward toward the Peruvian capital of Lima, while the Chilean fleet blockaded the main Peruvian port of Callao.

Although their advance was delayed by harassment from small allied forces, the Chileans were finally able to lay siege to Lima. The Chilean force occupied Lima at the end of October 1838 but abandoned it on November 3 on hearing of the approach of a large Bolivian army under General Santa Cruz. The Chileans withdrew by land and sea toward Huacho. However, Santa Cruz failed to exploit the Chilean retreat fully, despite successes in several small skirmishes culminating in a major Chilean reverse at Buín on January 6, 1839.

The resounding defeat of the Peruvian fleet at Casma by a smaller Chilean squadron under British admiral Roberto Simpson, on January 12, left Chile in absolute control of the southeastern Pacific. General Bulnes again assumed the initiative. After inflicting a crushing defeat on the Bolivian Army at Yungay on January 20, the Chileans commenced a second push southward, occupying Lima for the second time in April. Santa Cruz had already fled to Ecuador, and both the war and the short-lived Peru-Bolivia Confederation now came to an end.

After 1843, when Bulnes was president (1841-51), the Chilean Army concentrated on penetrating the area south of the Río Bío-Bío, still largely the domain of the Araucanian people. In response, the Araucanians rose in a bloody revolt, which was suppressed in 1859- 61, although the southern portion of the country remained largely outside the control of the national government.

In 1865, in a last attempt to reconquer their lost South American colonies, the Spaniards blockaded Chilean and Peruvian ports, an action that led to war between Spain and an ad hoc alliance of Chile, Bolivia, Peru, and Ecuador. Hostilities were confined to the sea. Although twenty-six years of freedom from external threat had once ag229 again seen the decline of the Chilean Navy, the blockade was effectively broken by the naval victory of the allied fleet, under the Chilean admiral Juan Williams Rebolledo, at Papudo on September 17, 1866. The naval war with Spain ended shortly afterward.

Data as of March 1994