Complex sentence: On 12 October 1851, Honório and an Uruguayan envoy signed a treaty in Rio de Janeiro setting the international border between Brazil and Uruguay, which included Uruguay abandoning some claims to disputed areas in exchange for Brazilian aid in the war against Argentina.
Split into simpler sentences: On 12 October 1851, Honório and an Uruguayan envoy signed a treaty in Rio de Janeiro setting the international border between Brazil and Uruguay. The agreement required Uruguay to abandon some claims to disputed areas in exchange for Brazilian aid in the war against Argentina.