reason to expect the Germans would not do the same with Oboe as soon as they detected the signals. Despite widespread opposition to the use of Oboe, A.P. Rowe ordered development to begin. Development began both on the 1.5 m wavelength shared by most early UK radar systems, but also at the new "fashionable" 10 cm microwave wavelength provided by the cavity magnetron. The latter would not only provide higher accuracy, but also be largely immune to jamming unless the Germans developed their own high-power microwave devices. This only occurred in the very last days of the war. Two stations were set up as far east as possible, one in Dover (Walmer) and a second in Cromer (RAF Trimingham). On any given mission, one of the stations would be Cat and the other Mouse. In early testing in September 1941, an aircraft flying along the arc from Dover demonstrated an accuracy of , better than any bombing method then in use. Accuracy with bombs was not quite as good, as the bombs themselves were not identical and had slightly different trajectories. In a demonstration for senior officials on 2 July 1942, the system demonstrated a real-world accuracy of . In contrast, even using advanced visual bombsights like the Norden, average accuracies in 1942 were on the order of . Oboe was first used in experimental operations by Short Stirling heavy bombers in December 1941, attacking Brest. These aircraft had a relatively limited service ceiling, and was limited to attacks at short-range where they maintained line-of-sight to the UK. At that time there was a great debate taking place in Bomber Command over the use of "pathfinders", specialized aircraft and crews that would find the targets and use flares to mark them for attack. The same technique had first been used during the Blitz by the Germans, notably by the specialist Kampfgruppe 100, but its effectiveness had been severely curtailed by British jamming efforts. Nevertheless, the concept had enough backing that a small force of Mosquitoes had been organized to operate as a pathfinder force, using normal optical sighting. This proved disappointing in practice, offering only a slight improvement in accuracy. But the Mosquitoes were also the only aircraft that had the performance to fly at altitudes at which the Oboe signals could be received over Germany. At a meeting in the summer of 1942, it was agreed that the pathfinder