<P> In 1849 Austria sent unmanned, bomb - filled balloons to attack Venice . UAV innovations started in the early 1900s and originally focused on providing practice targets for training military personnel . </P> <P> UAV development continued during World War I, when the Dayton - Wright Airplane Company invented a pilotless aerial torpedo that would explode at a preset time . </P> <P> The earliest attempt at a powered UAV was A.M. Low's "Aerial Target" in 1916 . Nikola Tesla described a fleet of unmanned aerial combat vehicles in 1915 . Advances followed during and after World War I, including the Hewitt - Sperry Automatic Airplane . The first scaled remote piloted vehicle was developed by film star and model - airplane enthusiast Reginald Denny in 1935 . More emerged during World War II--used both to train antiaircraft gunners and to fly attack missions . Nazi Germany produced and used various UAV aircraft during the war . Jet engines entered service after World War II in vehicles such as the Australian GAF Jindivik, and Teledyne Ryan Firebee I of 1951, while companies like Beechcraft offered their Model 1001 for the U.S. Navy in 1955 . Nevertheless, they were little more than remote - controlled airplanes until the Vietnam War . </P> <P> In 1959, the U.S. Air Force, concerned about losing pilots over hostile territory, began planning for the use of unmanned aircraft . Planning intensified after the Soviet Union shot down a U-2 in 1960 . Within days, a highly classified UAV program started under the code name of "Red Wagon". The August 1964 clash in the Tonkin Gulf between naval units of the U.S. and North Vietnamese Navy initiated America's highly classified UAVs (Ryan Model 147, Ryan AQM - 91 Firefly, Lockheed D - 21) into their first combat missions of the Vietnam War . When the Chinese government showed photographs of downed U.S. UAVs via Wide World Photos, the official U.S. response was "no comment". </P>

What is the size of a military drone