He expelled one President, converted the other into a passive instrument of his will, declined to promulgate a constitution that the Congress had prepared, and, after obtaining from that body an appointment to supreme command, dissolved the Congress without further ado.

Unfortunately none of these radical measures had any perceptible effect upon the military situation.

Though Bolivar gathered together an army made up of Colombians, Peruvians, and remnants of San Martin's force, many months elapsed before he could venture upon a serious campaign.

Then events in Spain played into his hands.

The reaction that had followed the restoration of Ferdinand VII to absolute power crossed the ocean and split the royalists into opposing factions.
Quick to seize the chance thus afforded, Bolivar marched over the Andes to the plain of Junin.