Editing Night fighter (section)

===Interwar period===
With little money to spend on development, especially during the [[Great Depression]], night-fighting techniques changed little until just prior to [[World War II]].

In the meantime, aircraft performance had improved tremendously; compared to their First World War counterparts, modern [[bomber]]s could fly about twice as fast, at over twice the altitude, with much greater bomb loads. They flew fast enough that the time between detecting them and the bombers reaching their targets left little time to launch [[interceptor aircraft|interceptors]] to shoot them down. Higher altitude bombers also required extremely large and heavy [[antiaircraft gun]]s to attack them, badly limiting the number of guns available.  At night, or with limited visibility, these problems were compounded. The widespread conclusion was that "[[the bomber will always get through]]", and the [[Royal Air Force]] invested almost all of their efforts in developing a night bomber force, with the Central Flying School responsible for one of the most important developments in the period by introducing "[[Instrument flight rules|blind flying]]" training.<ref>Robinson 1988, p. 24.</ref>

The [[Spanish Republican Air Force]] used some [[Polikarpov I-15]]s as night fighters. Pilot José Falcó had equipped his fighter with a radio receiver for land-based guidance for interception. One of the I-15s configured for night operations, fitted with tracer and explosive .30 rounds, scored a daylight double victory against Bf 109s in the closing stages of the war.<ref>Lázaro, Carlos. [http://adar.es/index/index.php?option=com_content&task=view&id=91 "Los chatos noctumos" (in Spanish)] {{Webarchive|url=https://web.archive.org/web/20091228161948/http://adar.es/index/index.php?option=com_content&task=view&id=91 |date=28 December 2009 }} ''Adar.'' Retrieved: 4 August 2013.</ref>

Nevertheless, some new technologies appeared to offer potential ways to improve night-fighting capability. During the 1930s, considerable development of [[infrared detector]]s occurred among all of the major forces, but in practice, these proved almost unusable. The only such system to see any sort of widespread operational use was the Spanner Anlage system used on the [[Dornier Do 17]]Z night fighters of the [[Luftwaffe]]. These were often also fitted with a large IR searchlight to improve the amount of light being returned.<ref>Henini and Razeghi 2002, p. 128.</ref>

Immediately prior to the opening of the war, [[radar]] was introduced operationally for the first time. Initially, these systems were unwieldy, and development of IR systems continued. Realizing that radar was a far more practical solution to the problem, [[Robert Watson-Watt]] handed the task of developing a radar suitable for aircraft use to [[Edward George Bowen|'Taffy' Bowen]] in the mid-1930s. In September 1937, he gave a working demonstration of the concept when a test aircraft was able to detect three [[Home Fleet]] [[capital ship]]s in the [[North Sea]] in bad weather.<ref>Robinson 1988, p. 34.</ref>

The promising implications of the test were not lost on planners, who reorganised radar efforts and gave them increased priority. This led to efforts to develop an operational unit for aircraft interception (AI). The size of these early AI radars required a large aircraft to lift them, and their complex controls required a multiperson crew to operate them. This naturally led to the use of [[light bomber]]s as the preferred platform for aircraft interception radars, and in May 1939, the first experimental flight took place, on a [[Fairey Battle]].<ref>Robinson 1988, p. 28.</ref>