The interception of the Rex was a training exercise and military aviation achievement of the United States Army Air Corps prior to World War II. The tracking and location of an ocean-going vessel (the Italian liner SS Rex) by B-17 Flying Fortresses on 12 May 1938 was a major event in the development of a doctrine that led to a United States Air Force independent of the Army. The mission was ostensibly a training exercise for coastal defense of the United States, but was conceived by planners to be a well-publicized demonstration of the capabilities of "heavy bombers (as) long range instruments of power".
The flight was conducted during coastal defense maneuvers held by the Air Corps without the participation of the United States Navy, and apparently without understanding of their purpose by the Army Chief of Staff. Both had continuing disagreements with the leaders of the Air Corps over roles and missions, with the Navy disputing its maritime mission and the Army seeking to limit its role to that of supporting ground forces.
With a characteristic flair for creating publicity, the Air Corps' General Headquarters Air Force (its combat organization) not only successfully made the interception at sea, but exploited both live radio news coverage and dramatic photographs. Although the publicity resulted in a short-term setback for Air Corps ambitions, within a year both U.S. President Franklin D. Roosevelt and future Army Chief of Staff George C. Marshall became new proponents of long-range air power.
Background
Ostfriesland
In July 1921, promoting the concept of an independent Air Force, Gen. Billy Mitchell staged a series of aerial bombing exercises that resulted in the sinking of the former German battleship Ostfriesland by the U.S. Air Service. Incurring the enmity of the Navy, which considered the achievement nothing more than a publicity stunt, Mitchell continued to discredit the battleship as the main weapon for projection of power by sinking several more obsolete ships in the next two years. However, the Air Service was limited by Army policy to being an auxiliary of the ground forces and was unable to obtain a role that would use long distance bombers.
The "Shasta Disaster" When the Air Service was renamed the Air Corps in 1926, the Joint Army-Navy Board was in the process of reconsidering service responsibilities in coastal defense. Both Chief of Air Corps Major General Mason Patrick and Rear Admiral William A. Moffett, Chief of the Navy's Bureau of Aeronautics, resisted any restrictions on range or missions for their respective services' aircraft. The resulting Joint Action statement was vague regarding Air Corps actions over water but "left the door open" for the Navy's interpretation of its own authority, which was that the shore-based coastal patrol mission was its prerogative. Efforts by the War Department to clarify the issue were rebuffed by the Navy to the extent that the Secretary of War warned President Herbert Hoover in 1930 that the situation was endangering national defense.
On 7 January 1931, Army Chief of Staff Gen. Douglas MacArthur and Navy CNO Adm. William V. Pratt reached an agreement modifying the Joint Action statement by assigning the coastal defense role for land-based aircraft to the Air Corps. This came at a time when the Air Corps was seeking a mission to justify the development of all-metal monoplane bombers, and theorists at the Air Corps Tactical School were advocating the use of long-range heavy bombers. In August of that year, to garner publicity and generate favorable public opinion, Lt.Col. Frank M. Andrews, on the staff of outgoing Chief of the Air Corps Maj. Gen. James Fechet, proposed to bomb another ship during joint maneuvers with the Navy off the coast of North Carolina. Before the mission Col. Roy Kirtland, the base commander at Langley Field, cautioned reporters that the operation was to be only a bombing exercise using small bombs, and that "nothing spectacular" should be expected.