Three 5,000 cubic feet Nurse Balloons in Hangar. Fort Sill, Oklahoma, May 1, 1918. Nurse balloons were used to carry extra gas for inflating other balloons. Aviation at Fort Sill added lighter-than-air ships to its inventory when Company A, 1st Balloon Squadron, arrived on September 5, 1917 from the Balloon School in Omaha, Nebraska. In order to meet the demand for trained aerial observers for field artillery, a Balloon Corps Training School was set up at Post Field in 1918. During World War I, the school trained 751 officers and created 89 companies, of which 33 were deployed to Europe. Observation balloons are balloons that are employed as aerial platforms for intelligence gathering and artillery spotting. Their use began during the French Revolutionary Wars, reaching their zenith during World War I. Both the Allies and Germany employed balloons, generally a few miles behind the front lines. The balloons were fabric envelopes filled with hydrogen gas, whose flammable nature led to the destruction of hundreds of balloons on both sides.