Along with others, Ryan participated in the Spanish Civil War on the Popular Front side, fighting for the Comintern-organised International Brigades (retroactively known as the Connolly Column). After being captured by pro-Nationalist Italians, he was sentenced to death but later granted an 'escape' by Franco personally. He was released into the hands of the "Abwehr" (military intelligence of Germany) and transported to Berlin. Ryan spent the rest of World War II until his 1944 death working as an IRA–Abwehr go-between on operations such as "Dove", "Whale" and "Sea Eagle".