Pressing his advantage, the marquis began organizing an assault on the new Paraguayan defenses which López had thrown up along the Pikysyry, south of Asunción (Paraguay's capital). This stream afforded a strong defensive position which was anchored by the Paraguay River and by the swampy jungle of the Chaco region, both considered to be nearly impassable by a large force. Rather than making a frontal attack on López's line, Caxias had a road cut through the Chaco. The road was finished by early December, allowing the allied forces to outflank the Paraguayan lines and attack from the rear. In three successive battles (Ytororó, Avay and Lomas Valentinas) which became known as "Dezembrada" (Deed of December), the combined allied forces annihilated the Paraguayan army. López barely managed to escape with a few followers, and on 1 January 1869, the Brazilians occupied Asunción. According to historian Ronaldo Vainfas, Caxias' "performance ahead of the allied forces contributed in an unquestionable way to the final triumph over the enemy."