the 17 years long rule of rosas was influenced by permanent warfare, both from unitarians and by other countries. the peru–bolivian confederation, allied with france, declared the war of the confederation against argentina and chile; france supported it by imposing a naval blockade over buenos aires, which was maintained even after the peru-bolivian defeat. the french helped fructuoso rivera to oust the uruguayan president manuel oribe from power, so that rivera helped them against rosas. france gave up the blockade, but rosas still supported oribe in the uruguayan civil war to reestablish his rule in uruguay. the conflict against rivera led to a renewed conflict with france, this time allied with britain. the anglo-french blockade of the río de la plata was defeated as well. justo josé de urquiza, governor of entre ríos, thought by then that it was the time required by the federal pact to establish a constitution, but rosas still kept his idea of doing it after all provinces had already organized themselves. with the bulk of the army of the confederation on his side, and some allies, urquiza defeated both the army of oribe laying siege to montevideo and then rosas himself, in the battle of caseros.