Maskirovka (маскировка), which means disguise, concealment, or deception was actually a pretty big part of Soviet military doctrine during World War II. We don't typically think of Soviet military doctrine in those terms; indeed, 'Soviet military doctrine' as a concept during the Second World War usually conjures up a joking, 'heh heh, you mean human waves of underarmed Communists charging that well-oiled fighting machine, the Wehrmacht?' which is more associated with maskirovka's more famous sibling Deep Operations (which that description doesn't accurately describe either of course). But in fact, maskirovka was essential to Soviet military strategy and contributed not insignificantly to concealing troop movement and location, combat readiness and potential effectiveness, and probably most shockingly (given the sheer size of the Red Army), aided in launching surprise attacks.
So what did that actually look like? Pavel Melnikov, who was a divisional commander during WWII (one of the youngest as well considering he was born February 1919, making him 22 when the war broke out in the Soviet Union) who went on to become the chief of the M.V. Frunze Military Academy in 1978, described early use of maskirovka thus:
[T]he creation of attack groupings at a considerable distance from the front line or to one side of the planned main axis of attack; accomplishment of troop regrouping only at night and their advance to initial areas for an offensive over a one or two day period; constantly preserving the established routine in areas where attacks were planned; conduct of reconnaissance across a broad front extending beyond the limit of where the main attack was to be delivered; reliable screening of the area for concentration of the main grouping against enemy ground and aerial reconnaissance; and the attack by troops from the move. (see pp. 51, Hamilton)
So you've got your standard 'only regroup or move at night' there as well as 'don't obviously gather troops at the site of a planned maneuver,' but because the Soviets were such a massive military force the use of offensive feigning was likewise significantly more potent when a westward thrust from the north could require that you maneuver in such a way that you expose your southern position to a separate attack-- and if that northern thrust turned out to be maskirovka then you're in big trouble now aren't you?
Hamilton notes:
Of particular importance to the Soviets [...] was the experience they gained in simulating troop concentrations.
Another important factor to consider here is that during the early parts of the war as experienced by the Soviet Union, the Red Army was on the back foot in a big way. Operation Barbarossa (Hitler's ill-fated attack on his de facto allies in Moscow) was more or less a surprise offensive. I qualify that statement because Stalin had reliable intelligence informing him that indeed the Germans were on the march eastward and indeed it was not simply a training exercise and indeed the Soviets needed to prepare now. Stalin didn't just ignore these requests to order immediate mobilization-- he rejected them as invalid and called their author a few impolite words to boot. ^([3])
If we view the war in the east as having three phases (defense, attrition, offense), maskirovka is shown to actually have contributed quite heavily to turning the tide of war against Hitler's Wehrmacht (obviously including a whole litany of other factors). The first stage defense occurred up until around about the Battle of Moscow broke out (September 1941, 4 months into the war) when the Nazis were basically on an effectively unchallenged march into Soviet territory, the second stage attrition can be placed as having begun with the Battle of Stalingrad (July 1942, 13 months into the war) when the so-called blitzkrieg lightning strike had faltered and the Nazis had to face the harsh reality of a long war against the Soviet Union, and the third stage offense can be represented by the beginning of Germany's Operation Citadel and the Battle of Kursk (July 1943, 25 months into the war) when the German eastern offensive was halted once and for all and the slow crush of inevitable defeat began as the Red Army regained more and more of their former territory during their roughly two-year countermarch back to Berlin. Maskirovka was thus, far more impactful in the second and third phases I enumerated above for obvious reasons.
Once the Soviets had reached the attrition phase of the rough timeline I provided above, they employed dedicated staff to innovate, manage, and execute their maskirovka activities:
More specifically [...] characterized by a transition from the employment of individual, separate deception measures to the use of a whole complex of measures, orchestrated to support large-scale operations. Of particular importance in allowing this transition was the fact that the Soviets now had more time to prepare their plans which, in turn, became much more detailed and sophisticated. One other important accomplishment during this stage was the creation of special staffs to plan and oversee the implementation of deception operations. (see pp. 51, Hamilton)
As /u/hamiltonkg notes, the Soviets integrated deception or maskirovka into their military doctrine at a very foundational level, to a much greater extent than their contemporaries. There is much to be said on the use of deception in other WWII militaries, to say nothing of the other four thousand or so years of historical warfare. But, maskirovka and operational art are what I know, so other flairs will have to tackle those worthy subjects.
Before adding my own two cents, though, I would also like to push back a little on aspects of /u/hamiltonkg’s answer. There are parts of it, particularly regarding the assumptions & analysis of David Hamilton’s Naval Postgraduate School thesis, which - with no disrespect intended to hamiltonkg’s recognized expertise as a flair - I find to be problematic and not reflective of the qualitative shift in English-language Soviet military studies that started in the mid 80s and accelerated in the 1990s after the fall of the USSR.^(1) Hamilton’s thesis contains a perceptible current of what I think we can call a sort of Orientalism - see for instance footnote 1 p.8, footnote 5 p.39, as well as his heavy citation of the Mongol influence claims of Pipes & Stinemetz. Don’t get me wrong - as those who are familiar with some of my previous answers on this sub may know, I am all about that strategic cultures/mentalités approach to military history. But, in this case I am cautious given the history of this type of racialized discourse in regards to Western perspectives on Russia and the Russian military (Franz Halder could have written some of the footnotes in this thesis, to be blunt about it.) Richard Pipes is also a polarizing figure in Soviet studies; the particular book quoted here (Survival is Not Enough) reads as an explicitly anticommunist polemic, seeing as it was written as policy prescription first, historical analysis second.^(2) I’m hesitant to reject the Mongol influence claims wholesale though, as Hamilton also cites Chris Bellamy’s RUSI article “Heirs of Genghis Khan: The Influence of the Tartar-Mongols on the Imperial Russian and Soviet Armies,” which presents the thesis in a much less racialized light. Bellamy, who is a fairly well-regarded historian of the Soviet military, traces the apparent Mongol influence through Russian military history with concrete examples, including - crucially - examples where historical Russian figures describe themselves explicitly drawing on Mongol concepts & practices.
Leaving the source-critique thread behind now^(3) and shifting to the matter of ‘pure’ military history, what did Red Army maskirovka look like? This section will pull heavily from David Glantz’s 1987 article “The Red Mask: The Nature and Legacy of Soviet Military Deception in the Second World War,” as it is long and fairly comprehensive for a journal article (though hopefully my copy of his book on the same topic will arrive soon from Amazon!) During the prewar years and even through the start of the war, the Soviets mostly limited themselves to deception and surprise at the tactical & operational levels of war.^(4) Deception in the Soviet conception was essentially the means to the desired end of surprise (vnezapnost). Surprise was highly desirable for its ability to disrupt enemy planning and sever effective communications between the front lines & higher command, thereby contributing to the supreme goal of Soviet operational maneuver - shock, or udar.^(5) Strategic surprise was generally discounted as impossible to achieve, owing to the difficulty of concealing the presence and intention of such a large fighting mass, although some did consider the possibility of achieving strategic surprise with highly mobile modern formations. The 1936 Field Regulations (PU36) describe the requirements of surprise at all levels thusly:
”Surprise action depends on concealment and speed, which are achieved by swift maneuver, secret concentrations of forces, concerted preparation of artillery concentrations, opening of surprise artillery fires, and by launching unexpected infantry (cavalry), tank, and air attacks ...Surprise is also achieved by the unexpected employment of new military weapons and new combat tactics.”
In terms of concrete tactical measures, this meant things like fake fortifications, decoy artillery barrages on targets they did not actually intend to assault, fake encampments in the woods, fake ‘parties’ with loud music to cover the sound of engines running, and the extremely cautious concealment of the real force of troops by methods like light and noise discipline and careful camouflage. As the Soviets learned later in the war, it also meant not being too careful with your camouflage. Sudden radio silence or the cessation of scouting operations on a major operational axis could tip off the defenders. Tank engines would often be left running at night, or the tanks would drive around in circles, to give the impression of large tank concentrations at feint locations. Maskirovka included aggressive patrolling and air defense to deny enemy reconnaissance patrols & flights, too, as well as comprehensive covering of roads and rail networks with barricades & fake tree cover (or sometimes relocated real tree cover) to keep enemy observers from taking note of traffic. The preparations for the Manchurian Strategic Offensive in 1945 included covering hundreds of miles of railway in this manner, so as to conceal the 1.5 million-troop buildup required for the operation. The Soviet theorist Krasil’nikov summed up measures for rapid and secretive concentration of forces thusly:
”1. Air reconnaissance must be conducted with accustomed intensity and on usual directions.
Divisions located at the front must, in no circumstances, be changed with new ones before the completion of an operational deployment.
Radio transmissions must remain normal and can conform sometimes to the radio deception of the enemy (disinformation of a plausible character).
Secrecy of upcoming operations is maintained from forces and staff.
Regrouping and transfer of forces at night, gradually and in small columns.
Operational deception of forces in the forward region is organized by means of creating false orders about the arrival of forces in the forward area and the covering of the real disposition of forces and by a series of other maskirovka measures.
The starting positions for the offensive are occupied not earlier than on the eve of the offensive.”
S.N. Krasil'nikov, Nastupatel'naya armeiskaya operatsiya (The army offensive operation), (Moscow: Voenizdat, 1940), reprinted in Voprosy strategic i operativnogo iskusstva v sovetskikh voennykn trudakh (1917-1940 gg) (Questions of strategy and operational art in Soviet military work (1917-1940), (Moscow: Voenizdat, 1965), p.490.
Maskirovka was not limited to camouflage, radio discipline, and counter-recce actions, however. Maskirovka extended into the operational (and later in the war, strategic) spheres, for which the aforementioned actions were necessary building blocks. Whereas these building blocks focused on misleading the enemy as to the number, exact position, combat power, and intentions of local combat forces, operational deception focused on misleading the enemy as to the overall timing, location, and intentions of major offensives. Large, seemingly committed offensives in other sectors served to hide the location of the intended ‘real’ offensive. For instance, the Soviets at least claimed that the costly battles around Rzhev and Vyazma in the summer and fall of 1942 were an intentional diversion from the real target of Stalingrad. The historiography on this is not clear, but it would be consistent with the generally thorough maskirovka actions taken in preparation for the Operation Uranus counterattack at Stalingrad that winter.^(6)
I want to meander a little here because Stalingrad is, in general, a good case study in the early maturation of maskirovka. In addition to careful hiding of the troop and materiel concentrations, the Soviet High Command (Stavka) limited planning to a very tightly controlled group of senior commanders. No written communiques were sent from Stavka to army and front commanders; all orders and discussions took place in person, and front commanders were only read into the plans a couple of weeks before Uranus. Troops were moved exclusively by night, except for of course some decoy formations which moved away from the breakthrough locations during the daytime. At higher levels, Soviet propaganda outlets intensified the defensive, not-one-step-back messaging around Stalingrad, indicating that the Red Army there was on the ropes and unable to mass forces for a major counterattack.
