During the Pikysyry campaign, the Paraguayan army was destroyed and later had to be rebuilt; the allied armies dawdled around Asunción after taking it in January 1869, as their commander, the Duke of Caxias had left the theater, and the soldiers themselves were tired and demoralized after years of campaigning around Humaitá.
This meant that operations were only resumed by May 1869, and then, only half-heartedly. The Pikysyry campaign's result meant that Paraguay no longer had the capacity to wage a regular war - the conlfict became irregular in nature and entered its last phase, the Campaign of the Hills.
In June 1869, allied troops were conducting raids around Quiíndy, Carapeguá and Acahay, where nowadays is the Paraguarí department, circa 100 km away from Asunción. Paraguayan president López, when informed of this, ordered general Bernardino Caballero to attack said troops. The Paraguayan column arrived at Ybytimí to find it deserted; they managed to track the allied troops down in Sapucaí, where 400 Paraguayan troops were ordered to lay in ambush against the enemy. When the Brazilian column entered the killing zone, the ambush was sprung, and the Paraguayans charged upon them starting a generalized melee. Soon afterwards, the Brazilians started to retreat towards Paraguarí. Another Paraguayan force had been posted in wait in that direction, however, 200 men under major Bernal, and they cut off the retreat. The Brazilians then changed course towards Tebicuary, which they managed to reach despite the harassment from Bernal's men.
Caballero's troops then returned to the headquarters in Azcurra.
Paraguay
Empire of Brazil