Dvorak served with the American Army Field Artillery during the punitive expedition against Pancho Villa and was wounded during the campaign. Afterward he was discharged and enlisted in the United States Naval Reserve, teaching mathematics and navigation until World War I, during which he served aboard the captured German privateer USS "Callao" bringing troops home until his discharge in 1919. Later, he was the captain of a "Gato"-class submarine in the United States Navy during World War II. While his name is pronounced ), with the "ř" roughly as a simultaneous trilled and due to him being of Czech descent, Dvorak's family in the U.S. pronounces it , with an English "r."