▁by ▁Brazil , ▁Boliv ia , ▁Uruguay , ▁France ▁and ▁the ▁UK , ▁as ▁well ▁as ▁other ▁Argent ine ▁fa ctions ▁during ▁the ▁Argent ine ▁Civil ▁Wars . ▁ ▁Ros as ▁was ▁ou sted ▁from ▁power ▁in ▁ 1 8 5 2 ▁by ▁Just o ▁José ▁de ▁Ur qu iza , ▁after ▁the ▁battle ▁of ▁Cas eros . ▁Ur qu iza ▁conven ed ▁the ▁ 1 8 5 3 ▁Const itu ent ▁Assembly ▁to ▁write ▁a ▁national ▁constitution . ▁Buenos ▁Aires ▁resist ed ▁Ur qu iza ▁and ▁se ced ed ▁from ▁the ▁Confeder ation ▁in ▁ 1 8 5 2 , ▁becoming ▁the ▁State ▁of ▁Buenos ▁Aires ; ▁the ▁province ▁would ▁return ▁to ▁Argentina ▁in ▁ 1 8 6 1 . ▁ ▁History ▁ ▁Administration ▁of ▁Juan ▁Manuel ▁de ▁Ros as ▁Modern ▁Argentina ▁is ▁a ▁small ▁subset ▁( approx . ▁ 1 / 3 ) ▁of ▁the ▁Vic ero yal ty ▁of ▁the ▁Río ▁de ▁la ▁Pl ata , ▁a ▁col ony ▁of ▁Spain ▁which ▁also ▁included ▁present - day ▁Boliv ia , ▁Uruguay , ▁part ▁of ▁Peru ▁and ▁most ▁of ▁Par agu ay . ▁Long ▁after ▁att aining ▁independence , ▁Argentina ▁attacked ▁and ▁conquer ed ▁large ▁areas ▁of ▁ind igen ous ▁land . ▁ ▁The ▁May ▁Revolution ▁in ▁Buenos ▁Aires ▁began ▁the ▁Argent ine ▁War ▁of ▁Independ ence , ▁and ▁the ▁country ▁was ▁renamed ▁the ▁United ▁Provin ces ▁of ▁the ▁Río ▁de ▁la ▁Pl ata . ▁Modern ▁Boliv ia ▁and ▁Par agu ay ▁were ▁lost ▁during ▁the ▁conflict ▁and ▁became ▁new ▁states