In the Battle of Acosta Ñu, Paraguayan forces consisting of 500 adult men and about 3,500 children fought 20,000 Brazilian and Argentinian soldiers. Some boys had to wear fake beards to disguise their young age. The battle resulted in the decisive Allied victory. About 2,000 Paraguayan children were killed in action, and 1,200 were taken prisoner and then executed.
Paraguayan Children's Day was establish to honor the memory of the children who lost their lives in the Battle of Acosta Ñu. Despite the tragic background of the holiday, it is marked not only with mourning ceremonies, but also with entertaining activities for children.