Instead of advancing to the capital, already evacuated and bombarded, Caxias went south and attacked the Paraguayans from the rear in December 1868, in an offensive which became known as "Dezembrada". Caxias' troops were ambushed while crossing the Itororó during an initial advance, during which the Paraguayans inflicted severe damage on the Brazilian armies. But days later the Allies destroyed a whole Paraguayan division at the Battle of Avay. Weeks later, Caxias won another decisive victory at the Battle of Lomas Valentinas and captured the last stronghold of the Paraguayan Army in Angostura. On 24 December, Caxias sent a note to Solano López asking for surrender, but Solano López refused and fled to Cerro León. Alongside the Paraguayan president was the American Minister-Ambassador, Gen. Martin T. McMahon, who after the war became a fierce defender of López's cause.