 Only the question of the "Chaco Boreal" (Northern Chaco) was left unresolved.Brazil had signed the separate Loizaga – Cotegipe Treaty with Paraguay in 1872 and now did much to help Paraguay in its negotiations with Argentina.Paraguay, with Brazilian support, refused to give up Chaco territory, and both sides agreed to international arbitration by US President Rutherford B. Hayes, who, on November 12, 1878, decided in favor of Paraguay.