His education was continued by the Sulpicians at St. Charles College in Ellicott City, Maryland, and St. Mary's Seminary in Baltimore.
[1] A week after he was ordained, Byrne was given permission by Cardinal James Gibbons to enter Maryknoll.
[1] He supervised construction projects at Maryknoll and at Scranton, Pennsylvania, and then served as the rector of both seminaries.
[1] He made radio broadcasts on behalf of the United States Army to calm the Japanese people as the Americans occupied Japan at the conclusion of the war.
Pope Pius XII appointed Byrne Apostolic Visitor of the Holy See to Korea on July 17, 1947.
[5] On April 7, 1949, Pope Pius named him the Titular Bishop of Gazera and the first Apostolic Delegate to Korea.