Service in World War I came before college, and John Mathews became a flight instructor and second lieutenant after time in the cavalry. Afterward, he went to the University of Oklahoma, graduating with a degree in geology. He studied (at his own expense) at Oxford University in England, graduating in 1923 with a degree in natural science. He also studied international relations at the University of Geneva and the Graduate Institute of International Studies. In addition, he traveled in Africa before returning to the United States, determined to study the culture and traditions of the Osage.