On 16 April 1869, Prince Gaston, Count of Eu took command of the Allied Army Headquarters in Luque, two days after his arrival in Asunción.

[1]: 99–100 Since Paraguayan President López refused to surrender, the Allies installed a triumvirate in Asunción made of two elderly former exiles, Carlos Loizaga and José Diaz de Bedoya, along with a young ex-soldier turned spy, Cirilo Antonio Rivarola, and decided to continue the war.

López decided to resist the Allies in the mountainous region of Northeastern Paraguay.

López organized a force of 9,000 men and boys from his headquarters in Cerro León.

The last major battle, in which Bernardino Caballero (who later became President of Paraguay) fought a Brazilian-Argentine combined force of 20,000 under Emperor Pedro II's son-in-law Prince Gaston and future Brazilian president Manoel Deodoro da Fonseca.