Wireless operators at work at the headquarters of the Nikita Khrushchev partisan detachment.

Already during the first weeks of the Germano-Soviet war first reconnaissance and subversive units were parachuted in the enemy rears or transferred across the frontlines in order to carry intelligence operations on behalf of the special cells of the General Staff, fronts and armies, as well as autonomous specialized units organized in the "Big Land". First groups started operating in Lithuania and White Russia, as well as in eastern Poland. The latter included Poles, veterans of the Polish campaign 1939 and interned in the USSR. Those recruited for the Soviet intelligence, were trained in the intelligence centre Skhodnya near Moscow.

At the night from 16 to 17 September 1941 in the German rears in the vicinity of the lake Domzheritskoye (the basin of the river Berezina), some 18-20 kilometres from the town of Lepel (province of Vitebsk), landed a 55-men strong airborne special operations partisan detachment commanded by Col. Grigoriy Linkov (Batya). This detachment played a significant role in flaring up the partisan war in Byelorussia and in the north-west areas of the Ukraine. It was created in Moscow by the Chief Intelligence Executive (Glavnoye Razvedyvatelnoye Upravleniye - GRU) of the General Staff of the Red Army. There Linkov created the nucleus of the Central Intelligence Base, which reported directly to the Chief Intelligence Executive of the General Staff in Moscow.

In the beginning of 1942 from the airfield Vnukovo near Moscov took off 11 reconnaissance and sabotage groups, which were parachuted in the Western Ukraine and Byelorussia. Among them was an 18-men group under the command of the famous Soviet skater Konstantin Kudryavtsev (Volodya). The group made its base in the vicinity of the town Vasilishki, but operated in the whole province of Grodno, and used to meke incursions to Poland and even East Prussia.

In the summer of 1942 near Bereza-Kartuzskaya in the province of Brest landed another group trained in Skhodnya under the command of Capt. Yosif Topkin and Capt. Vasiliy Tsvetkov. Among other special groups and detachments parachuted in the enemy rears the group under the command of Col. Dmitry Medvedev, parachuted in the spring of 1942 in Volhynia. The group grew to hundreds of partisans and operated in the forests around Rovno. Medvedev's main task was to penetrate the seat of the Reich's commissar of the Ukraine Gauleiter Erich Koch. To do that to Rovno was sent a partisan, who perfectly spoke German language and knew German culture. His name was Nikolay Kuznetsov. He created a special intelligence group inside the city, composed of Soviet citizens and Poles. Posing as Lieutenant, later Captain, Paul Siebert, he had for months infiltrated the German garrison with his people, who used to collect valuable information. Among others, he informed the Soviet command about the preparations for the German offensive on the Kursk Salient, and plans to eliminate the leaders of the anti-fascist coalition during the conference in Teheran. In the autumn of 1943 Kuznetsov's people made several bold, successful attempts on high-ranking German officers: judge and SA-Oberführer Alfred Funk, commander of special commando troops Maj.-Gen. Max Ilgen, high-ranking official of the Reich's Commissariat Ukraine Paul Dargel, and General Hermann Knuth, deputy Reich's Commissar for the Ukraine.

Another source of intelligence information were regiments of the Border Guards, which before the war served on the western frontiers of the Soviet Union. They formed groups and detachments, which were transferred to the deep enemy rears, where they used to attack German headquarters, destroy storages, blow up bridges, dismantle railways, but first of all collect information about deployed troops, their armament and fortifications.

In 1943, after Red Army's great successes on all the fronts, the Soviet command decided to intensify underground operations in Western Byelorussia and Ukraine. In the second half of 1943 there were parachuted groups under the command of Capt. Roman Romkowski (Ryszard), Mieczysław Lesz, Maj. Konstantin Gruzdev (Stoikiye Group) and Maj. Nikolay Khmelyevtsev (Dalniye Group). However, most of the intelligence data were coming to the "Big Land" from the partisan detachments, and underground cells in towns and cities. In 1942-1943 partisan brigades, groups and detachments worked intensively on expanding their intelligence operations. Each unit as a rule had a special intelligence cell to collect information. They focused on tracing transfers of the troops from one sector of the front to another, reinforcements from Germany, as well as from the West and the Balkans, identification of the cargo and destinations, detection of the airfields, storages, road and bridge constructions, etc.

In the autumn 1942 the partisan intelligence detected a massive transfer of the German forces to the East front: one armoured division, three infantry divisions, two alpine rifles divisiona and an SS cavalry division. In July 1942 the Bryansk Headquarters of the Partisan Movement through its intelligence network in towns and railway stations identified 160 military transports passing the railway node in Roslavl en route to Orel and Kursk - altogether 7 infantry divisions, 400 tanks, 160 guns, 1,600 trucks and lorries, and 33,000 tons of ammunition. Partisans of the province of Leningrad detected 197 enemy garrisons, 67 bases and storages, 35 airfields, and 12 headquarters. They also identified the headquarters of the Army Group North in Pskov.

During the battle of Dnieper towards the end of 1943, partisans scouted the enemy defences along the western banks of the Dnieper and Donets, as well as the German forces concentrated along Kharkov. Partisans of the province of Orel delivered detailed information about the German defences, troops, communications and airfields to the headquarters of the Bryansk Front.

Between January and May 1944, before the Red Army's major offensive in Byelorussia (commenced on 23 June 1944), partisans detected 27 headquarters, 193 military posts, 598 tactical units, and 36 airfields. They also scouted German defences around Minsk, Vitebsk, Orsha and Bobruisk, and got hold on 500 important documents, maps, operational orders and directives.

In 1944 the Soviet partisan movement spread into Poland and Czechoslovakia, which were soon to become the battleground of the progressing East front. Dozens of partisan units made their way to those areas on foot, while airborne reconnaissance groups were parachuted from the air. In the province of Lublin operated several partisan brigades from the Ukraine and Byelorussia, as well as several parachuted reconnaissance and diversion groups. In May 1944, in the south-western part of the province of Lublin, landed a group under the command of Lt.-Col. Valentin Pelikh (Galicki), who transformed his group into a special secret unit, which amalgamated several Polish and Soviet partisan detachments. Pelikh had made contacts with the Polish underground, and particularly with the commander of the Lublin District of the People's Army. His group had a long-range radio-station, through which the partisans were promptly informing the Soviet command about the moves of the German troops in the Polish territories, about the transports with troops, equipment and supplies for the front, fortification works, and the moods among the German soldiers.

On the turn on 1944 and 1945 intelligence services of the Red Army and other intelligence centres sent dozens of reconnaissance and sabotage groups to East Prussia, Pomerania, Silesia, Bohemia and Moravia, and even to the German territories beyond the River Oder.