Argentine War of Independence Chile, allied with the Mapuches. On April 4, Argentine Colonel Juan Gregorio de Las Heras had occupied Concepción, but the Royalists retreated to Talcahuano. In early 1818, Royalist reinforcements from the Viceroyalty of Peru arrived, commanded by general Mariano Osorio, and advanced towards the capital. San Martín then turned to scorched earth tactics and ordered the evacuation of Concepción, which he thought was impossible to defend. On 18 February 1818, the first anniversary of the battle of Chacabuco, Chile declared its independence from the Spanish Crown. On March 18, 1818, Osorio led a surprise attack on the joint Argentine-Chilean army,
Army of the North and 9 artillery pieces could not deal with the 5,100 royalists and 23 artillery pieces and had to escape with about 1,000 casualties, while the royalists only counted 32 dead. Objectives were not met and the provinces were left surrounded by potential enemies. British and French could arrive by sea, Portuguese from the East and Spaniards from the North. Had they conquered Upper Perú, the biggest threat, the royalists, would have been ended. In January 1816, Lieutenant Colonel Gregorio Aráoz de Lamadrid was sent to the north, but on 31 January was defeated at Culpina. On 2 February he won