On September 18, 1865, the surrender of the Paraguayan Lieutenant Colonel Antonio de la Cruz Estigarribia took place in the presence of Emperor Dom Pedro II of Brazil and the Presidents Bartolomé Mitre of Argentina and Venancio Flores in Rio Grande do Sul, thereby concluding the first phase of the Paraguayan War. Although the surrender could have marked the end of the conflict, Brazil insisted on the death of Solano López, prolonging the conflict further.

The surrender of Paraguay, marking the end of the first phase in the Paraguayan War
Capitulation of Paraguayans locked in the city of Uruguaiana (L’Illustration: journal universel, Vol. XLVII, nº 1.197, 1866)