if the intervention prevailed, Brazil would have neighbors even more powerful than the Confederation. Thus, he strongly advised against joining it, and restoring good relations with Rosas if possible. William Brent, representative of the United States in Buenos Aires and supporter of the Monroe Doctrine, supported Rosas in the dispute with the European powers, and proposed to act as mediator. After the victory at the battle of India Muerta, Oribe was about to enter to Montevideo. Brent proposed that he did so giving an amnesty to the supporters of Rivera, calling to elections in the Legislature, and then the Argentine forces supporting him should leave the country at that point. Oribe accepted, but the British arrived to Montevideo and refused to allow Oribe to enter to the city. Arana, Deffaudis and Ouseley rejected Brent's mediation, and gave an ultimatum: if the army of Oribe and the Argentine navy of William Brown did not leave Uruguay in ten days, they would proceed to block Buenos Aires. Beginning of armed actions The same night the ultimatum was issued, still during the ten days period, the British ship Cadmus and the French one D'Assas anchored next to the Argentine ships San Martín and 25 de mayo. William Brown requested permission to return to Buenos Aires, which was allowed but with the condition of delivering the British and French sailors. Brown requested permission to do so in Buenos Aires, as most of his crew was Irish, but received no answer. When he finally sailed back to Buenos Aires, he was attacked. The Anglo-French forced boarded and seized the complete Argentine navy, the ships San Martín, 25 de mayo, General Echagüe, Maipú and 9 de julio. The French raised their flag in the first two, and the British did so in the last three. The Argentine officers were returned to Buenos Aires, and William Brown and all the British sailors were forbidden to sail under the Argentine flag during the remainder of the conflict. The following day, the Anglo-French forces disembarked in Montevideo, reinforcing the defenses of the city. Since the defeat at India Muerta, the Montevidean defenders were less than 3 500. Rivera thanked these actions, saying that it secured the Uruguayan independence. Many politicians of Buenos Aires criticized them during a meeting in the Junta of Representatives in Buenos Aires. Rosas learned in 1838 that the Isla Martín García was difficult to defend,