The word "radar" stands for radio direction and range; that is, a device to use radio waves to determine not only the direction by using a narrow beam, and the range by timing the reflection back from the target, but also the velocity of the target by means of the Doppler effect. Heinrich Hertz, a German scientist, had established that radio waves were reflected by metal objects in 1885 and by 1933 the Germans secretly succeeded in using radar to detect ships in Kiel Harbour. In 1934 the British scientist Robert Watson-Watt began the development work that would give crucial warning of German aircraft attacks in the Battle of Britain. Commander William E. G. Taylor (Taylor, William E.G.), an American Naval Reserve officer, had been attached to the British Royal Navy for a year and to the Royal Air Force for another year prior to going to Hawaii in 1941 when, in the autumn, five mobile radar sets were acquired for use there. The Army Signal Corps was charged with establishing the system, known as the Air Warning Service. The National Park Service refused to allow a radar unit on top of Haleakala, the mountain on the island of Maui, but six locations were set up on Oahu: Fort Shafter, Opana, Kaala, Waianae, Kawailoa and Koko Head. Lieutenant General Walter C. Short (Short, Walter C.) commanded the army in Hawaii. Short had few men qualified to work the apparatus and he was also concerned that the equipment should not fail through over-use. He therefore ordered that radar should only be used between the hours of 0400 and 0700. This order was not changed even when, on 27 November, he received the message from General George C. Marshall warning him that Japanese hostile action was possible at any moment and directing him to undertake such reconnaissance and other measures as he deemed necessary. Soon after 0700 on 7 December Privates Joseph Lockard (Lockard, Joseph) and George Elliott (Elliott, George) observed a large "blip" on their radar showing a substantial body of aircraft approaching from the north. Their report was not acted on.