In 1925, the two ships were refitted, with the boilers being re-tubed and converted to use oil. In 1932, a war broke out between Peru and Colombia over territory in the Amazon rainforest. In May 1933, "Almirante Grau", escorted by two submarines, was sent via the Panama Canal to the mouth of the Amazon River to support operations by Peruvian warships on the Amazon. However, the war ended before they arrived, so "Almirante Grau" and the two submarines returned to the Pacific.