This was recognized in a 1938 truce , signed in Buenos Aires in Argentina .
This was approved in a referendum in Paraguay , by which Paraguay was awarded three - quarters of the Chaco Boreal , 20,000 square miles ( 52,000 km ) .
This was recognized in a 1938 truce , signed in Buenos Aires in Argentina and approved in a referendum in Paraguay , by which Paraguay was awarded three - quarters of the Chaco Boreal , 20,000 square miles ( 52,000 km ) .