The GRU is Russia's largest foreign intelligence agency. In 1997 it deployed six times as many agents in foreign countries as the SVR, the successor of the KGB's foreign operations directorate (PGU KGB). It also commanded 25,000 Spetsnaz troops in 1997.
The first Russian body for military intelligence was established in 1810 by the War minister Michael Andreas Barclay de Tolly who suggested to the Tsar the creation of a permanent body for Strategic military intelligence. In January 1810, The Expedition for Secret Affairs under the War Ministry was formed. Two years later it was renamed the Special Bureau.
In 1815, the bureau became the First Department under the General Chief of Staff. In 1836 the intelligence functions were transferred to the Second Department under the General Chief of Staff. After many name changes through the years, in April 1906 the Military intelligence was carried out by the Fifth Department under the General Chief of Staff of the War Ministry.
Its first predecessor in Soviet Russia was created on October 21, 1918 under the sponsorship of Leon Trotsky, who was then the civilian leader of the Red Army; it was originally known as the Registration Agency (Registrupravlenie, or RU). Simon Aralov was its first head. In his history of the early years of the GRU, Raymond W. Leonard writes:
As originally established, the Registration Department was not directly subordinate to the General Staff (at the time called the Red Army Field Staff – Polevoi Shtab). Administratively, it was the Third Department of the Field Staff's Operations Directorate. In July 1920, the RU was made the second of four main departments in the Operations Directorate. Until 1921, it was usually called the Registrupr (Registration Department). That year, following the Soviet–Polish War, it was elevated in status to become the Second (Intelligence) Directorate of the Red Army Staff, and was thereafter known as the Razvedupr. This probably resulted from its new primary peacetime responsibilities as the main source of foreign intelligence for the Soviet leadership. As part of a major re-organization of the Red Army, sometime in 1925 or 1926 the RU (then Razvedyvatelnoe Upravlenye) became the Fourth (Intelligence) Directorate of the Red Army Staff, and was thereafter also known simply as the "Fourth Department." Throughout most of the interwar period, the men and women who worked for Red Army Intelligence called it either the Fourth Department, the Intelligence Service, the Razvedupr, or the RU. As a result of the re-organization , carried out in part to break up Trotsky's hold on the army, the Fourth Department seems to have been placed directly under the control of the State Defense Council (Gosudarstvennaia komissiia oborony, or GKO), the successor of the RVSR. Thereafter its analysis and reports went directly to the GKO and the Politburo, apparently even bypassing the Red Army Staff.