had developed an acoustical unit that was used to aim a searchlight at targets. These techniques were impractical with aircraft that were above cloud or at a considerable distance; to overcome this, research was initiated on detection by electromagnetic means. Lieutenant-General M. M. Lobanov was responsible for these efforts in the GAU, and he thoroughly documented this activity later. Leningrad Most early work in radioobnaruzhenie (radio-detection) took place in Leningrad, initially at the Leningradskii Elektrofizicheskii Institut, (Leningrad Electro-Physics Institute, LEPI). Here, Abram F. Ioffe, generally considered the leading physicist in the Soviet Union, was the Scientific Director. The LEPI concentrated on radiating continuous wave (CW) signals, detecting the existence and direction of their reflections for use in early warning systems. While the GAU was interested in detection, the Voiska Protivo-vozdushnoi oborony (PVO, Air Defense Forces) was interested in determining the target range. Pavel K. Oshchepkov on the PVO technical staff in Moscow, strongly believed that the radiolokatory (radio-location) equipment should be pulsed, potentially allowing range to be determined directly. He was transferred to Leningrad to head a Special Construction Bureau (SCB) for radio-location equipment. To examine current and proposed detection methods, a meeting was called by the Russian Academy of Sciences; this was held at Leningrad on 16 January 1934 and chaired by Ioffe. Radio-location emerged as the most promising technique, but type (CW or pulsed) and wavelength (high frequency or microwave) were left to be resolved At the SCB, Oshchepkov's team developed an experimental pulsed radio-location system operating at 4 m (75 MHz.). This had a peak power of about 1 kW and a 10-μs pulse duration; separate transmitting and receiving antennas were used. In April 1937, tests achieved a detection range of nearly 17 km at a height of 1.5 km. Although this was a good beginning for pulsed radio-location, the system was not capable of measuring range (the technique of using pulses for determining range was known from probes of the ionosphere but was not pursued). Although he never created a range-finding capability for his system, Oshchepkov is often called the father of radar in the Soviet Union. As Oshchepkov was exploring pulsed systems, work continued on CW research at the LEPI. In 1935, the LEPI became a part of the Nauchno-issledovatel institut-9 (NII-9, Scientific Research Institute #9), one of several technical sections under the GAU. With M. A. Bonch-Bruevich as Scientific Director, research continued in CW