Vsevolod Nikolayevich (Boris) Merkulov (Всеволод Николаевич Меркулов in Russian) (27 November [O.S. 25 October] 1895 – 23 December 1953) was the head of NKGB from February to July 1941, and again from April 1943 to March 1946. He was a member of the so-called "Georgian mafia" of Lavrenti Beria, head of the NKVD.
Merkulov was born in 1895 at Zagatala in present-day Azerbaijan. In 1913, he graduated from the Tiflis Gymnasium with the gold medal and became a student at St. Petersburg University, Department of Physics and Mathematics. From 1921-1922, he worked as a detective at the Transportation Unit of the Cheka in Georgia. From 1925 to 1931, Merkulov held the posts of Head of Secret Operations Directorate and Deputy Head of GPU of Adzharistan.
Merkulov was People's Commissar of State Security of the USSR from 3 February 1941 until 20 July 1941, when the NKGB again fell under control of the NKVD as GUGB. From 1941 to 1943, Merkulov was Deputy People's Commissar of the NKVD. In 1943 the GUGB was again separated from the NKVD, and Merkulov became head of the NKGB from 20 July 1943 until 1946.
Vsevolod Merkulov was involved with a plan to build up a network of spies inside the Manhattan Project. The NKVD's first success was the recruitment of Klaus Fuchs. The project was given the codename "Enormoz". In November 1944 Pavel Fitin reported: "Despite participation by a large number of scientific organization and workers on the problem of Enormoz in the U.S., mainly known to us by agent data, their cultivation develops poorly. Therefore, the major part of data on the U.S. comes from the station in England. On the basis of information from London station, Moscow Center more than once sent to the New York station a work orientation and sent a ready agent, too (Klaus Fuchs)."