Irvine and his elder half-brother James Dunwoody Bulloch, who had served in the U.S. Navy for 14 years before joining a private shipping company, were both seafaring men. When the Southern states left the Union and the Civil War began in 1861, one of the first Union acts was to begin a strangling naval blockade on the Confederacy. With these developments, the two brothers decided to serve the southern cause.