In early May 1866, a Paraguayan attack at a marsh called Estero Bellaco failed. As the allies camped for over two weeks before resuming their advance, Paraguayan leader Francisco Solano López ordered a May 24 surprise attack on Tuyutí, a "a swampy, scrub-brush savannah". The Paraguayans attacked in three columns, and soon the battle turned into "a series of charges and countercharges, a Latin American version of Waterloo". The Paraguayan columns continued to attack, but never could overcome the allied firepower.