San Martin remained in Santiago only a short time after Chacabuco. Prepossessed with the idea that Chile could never be safe or Peru won until he had organised a fleet to wrest control of the Pacific from the Spaniards, he hastened across the Andes to arrange with his friends in the Argentine government for the necessary money. The Chilean campaign had saved Buenos Aires from impending invasion; the Argentine patriots would certainly be crushed if Chile should fall back into Spanish hands; they could never feel secure so long as Peru and Bolivia remained royalist. The promises which he asked were readily given, on his agreeing that Chile should contribute three hundred thousand dollars toward the purchase of a squadron on the Pacific, and forty thousand for the support of the Argentine army on the Bolivian frontier, besides taking the responsibility of the pay and maintenance of the Army of the Andes. Argentina was to aid in purchasing the fleet and hold back the Spaniards on the Bolivian border.
San Martin returned to Chile, where he was shortly followed by an official representative of the Argentine government and the alliance created by Chacabuco received formal sanction. He found Chilean affairs in a very unsatisfactory condition. O'Higgins was hated by the powerful partisans of the Carreras, and distrusted by Chileans generally as too much under Argentine influence. His power really rested upon Argentine bayonets; his appointment of Quintana, an Argentine and San Martin's aide-de-camp, as acting dictator at Santiago was bitterly resented. San Martin's presence did something to allay the feeling, but as a matter of fact he had little sympathy for the Chilean people, being a man who despised the arts by which popularity is gained, and who made few friends. Meanwhile the three Carreras were actively plotting from their exile at Buenos Aires for the overthrow of O'Higgins and San Martin. Their friends and agents swarmed in Chile and preparations were made for a rising as soon as they should set foot in the country. The two younger brothers attempted to cross the Andes in disguise, but were detected and arrested at Mendoza. Quintana ordered the imprisonment of many persons suspected of being Carrera partisans, but his severe measures raised national feeling to such a height that it was thought safest to carry out San Martin's suggestion and appoint a Chilean as acting dictator in his stead.