The settlement was short-lived, and further difficulties culminated in civil war. Urquiza met the army of Buenos Aires, again led by Mitre, at Pavón (Sept., 1861). The battle was indecisive, but Urquiza withdrew from the field, leaving the victory with Mitre. He retired to Entre Ríos, where he ruled with patriarchal autocracy until his assassination.
As governor after 1860, he again assumed leadership when fresh difficulties led to open war in 1861. At Pavón he won a victory for Buenos Aires; he then assumed national authority. In Oct., 1862, Mitre was elected president, and national political unity was finally achieved; a period of internal progress and reform began.