the 5th Squadron (Observation) and two years later the 5th Observation Squadron. In May 1921, the 5th was attached to General Billy Mitchell's 1st Provisional Air Brigade at Langley Field, Virginia. From May to October 1921, the squadron and other units of the Air Brigade bombed battleships off the eastern seaboard. Mitchell was determined to prove airplanes could sink warships. In July, in the well known SMS Ostfriesland incident, brigade airplanes sunk a modern, German-made battleship. General Mitchell proclaimed the era of battleships had ended and the age of airpower had begun. On 1 August 1922, the 5th Observation Squadron joined with the 1st Observation Squadron to form the 9th Observation Group, today's 9th Operations Group and the 9th Reconnaissance Wing's predecessor. In 1928, the Army attached the 99th Observation Squadron to the 9th Observation Group and assigned the squadron to the group the following year. Throughout the 1920s and early 1930s the 5th flew routine observation and training missions and participated in air shows. Squadron pilots flew a variety of World War I-vintage aircraft, including the DH-4, O-1, O-2, A-3, B-6, and several others. In the mid-1930s, as tensions increased in Europe, the United States began to expand its air arm. On 1 March 1935, the Army re-designated the 5th Observation Squadron as the 5th Bombardment Squadron. Soon after the re-designation, the squadron received new Martin B-10 bombers. The B-10, a small bomber best suited for coastal defense, could out-fly the best Army pursuit plane of its day. In 1938, the 5th switched to the larger Douglas B-18 Bolo. World War II Sixth Air Force By November 1940 German U-boats actively patrolled waters off Central America near the Panama Canal. The Army dispatched the 9th Bomb Group to guard the canal. The 5th Bombardment Squadron deployed to Rio Hato Army Air Base, Panama with that Group on 13 November 1940, at which time it was designated as the 5th Bombardment Squadron (Medium), this being changed to (Heavy) five days later. Two B-18A Bolos of the unit made "training flights" through Central America commencing 12 January 1941, flying from Albrook Field in the Panama Canal Zone. Their route took them first to San Jose, Costa Rica, then to San Salvador, El Salvador, Guatemala City, Managua, Nicaragua and thence back to David Field, Panama and home to Rio Hato. Major General Sanderford Jarman, Commander of the Panama Coast Artillery Command, was