 The situation was unstable, however, and the signing of the Treaty of San Ildefonso on October 1, 1777 led to a clearer demarcation of dominions in South America.In 1762 after the surrender of Colonia del Sacramento, Pedro de Cevallos went to the Portuguese, demanding the "eviction of the Yacuí River and areas of Rio Pardo, Santo Amaro, Rio Grande, San Gonzalo, San Miguel and Chuy, as well as Martín García Island and Dos Hermanas Island.