Deep operation
History: 

Before deep battle: The Russian Empire had kept pace with its enemies and allies and performed well in its major conflicts up to the 19th century. However, despite some notable victories in the Napoleonic Wars (1803–1815) and in various Russo-Turkish Wars, defeats in the Crimean War (1853–1856), Russo-Japanese War (1904–1905), the First World War (1914–1918), and the Polish-Soviet War (1918-1921) highlighted the weaknesses in Russian and Soviet military training, organization, and methodology .
After the Russian Revolution of 1917, the new Bolshevik regime sought to establish an entirely new military system that reflected the Bolshevik revolutionary spirit. The new Red Army (founded in 1918) combined the old and new methods. It still relied on the country's enormous manpower reserves; however, the Soviet program to develop heavy industry, which began in 1929, also raised the technical standards of Soviet arms industries to the level of other European nations. Once that had been achieved, the Soviets turned their attention to solving the problem of military operational mobility.
Primary advocates of the development included Alexander Svechin (1878–1938), Mikhail Frunze (1885–1925), and Mikhail Tukhachevsky (1893–1937). They promoted the development of military scientific societies and identified groups of talented officers. Many of these officers entered the Soviet Military Academy during Tukhachevsky's tenure as its commandant in 1921–1922. Others came later, particularly Nikolai Varfolomeev (1890–1939) and Vladimir Triandafillov (1894–1931), who made significant contributions to the use of technology in deep offensive operations.

Roots of deep battle: In the aftermath of the wars with Japan as well as experiences gained during the Russian Civil War several senior Soviet Commanders called for a unified military doctrine. The most prominent was Mikhail Frunze. The call prompted opposition by Leon Trotsky.  Frunze's position eventually found favour with the officer elements that had experienced the poor command and control of Soviet forces in the conflict with Poland during the Polish–Soviet War. That turn of events prompted Trotsky's replacement by Frunze in January 1925.

The nature of this new doctrine was to be political. The Soviets were to fuse the military with the Bolshevik ideal, which would define the nature of war for the Soviet Union. The Soviets believed their most likely enemy would be the capitalist states of the west they had to defend themselves against before and that such a conflict was unavoidable. The nature of the war raised four major questions:

Would the next war be won in one decisive campaign or would it be a long struggle of attrition?
Should the Red Army be primarily offensive or defensive?
Would the nature of battle be fluid or static?
Would mechanized or infantry forces be more important?
The discussion evolved into debate between those, like Alexander Svechin, who advocated a strategy of attrition, and others, like Tukhachevsky, who thought that a strategy of decisive destruction of the enemy forces was needed. The latter opinion was motivated in part by the condition of the Soviet Union's economy: the country was still not industrialized and thus was economically too weak to fight a long war of attrition. By 1928 Tukhachevsky's ideas had changed: he considered that given the nature and lessons of World War I, the next major war would almost certainly be one of attrition. He determined, however, that the vast size of the Soviet Union ensured that some mobility was still possible. Svechin accepted that and allowed for the first offensives to be fast and fluid; but ultimately he decided that it would come down to a war of position and attrition. That would require a strong economy and a loyal and politically-motivated population to outlast the enemy.
The doctrine pursued by the Soviets was offensively oriented. Tukhachevsky's neglect of defense pushed the Red Army toward the decisive battle and cult of the offensive mentality, which along with other events, caused enormous problems in 1941.
Unlike Tukhachevsky, Svechin determined the next war could be won only by attrition, not by a single or several decisive battles. Svechin also argued that a theory of alternating defensive and offensive action was needed. Within that framework, Svechin also recognised the theoretical distinction of operational art that lay between tactics and strategy. In his opinion the role of the operation was to group and direct tactical battles toward a series of simultaneous operational objectives along a wide frontage, either directly or indirectly, in order to achieve the stavka's ultimate strategic target(s). This became the blueprint for Soviet deep battle.
In 1929, Vladimir Triandafillov and Tukhachevsky formed a partnership to create a coherent system of principles from the concept formed by Svechin. Tukhachevsky was to elaborate the principles of the tactical and operational phases of deep battle. In response to his efforts and in acceptance of the methodology, the Red Army produced the Provisional Instructions for Organizing the Deep Battle manual in 1933. This was the first time that "deep battle" was mentioned in official Red Army literature.

Principles: 

Doctrine: Deep battle encompassed manoeuvre by multiple Soviet Army front-size formations simultaneously. It was not meant to deliver a victory in a single operation; instead, multiple operations, which might be conducted in parallel or successively, would induce a catastrophic failure in the enemy's defensive system.
Each operation served to divert enemy attention and keep the defender guessing about where the main effort and the main objective lay. In doing so, it prevented the enemy from dispatching powerful mobile reserves to the area. The army could then overrun vast regions before the defender could recover. The diversion operations also frustrated an opponent trying to conduct an elastic defence. The supporting operations had significant strategic objectives themselves and supporting units were to continue their offensive actions until they were unable to progress any further. However, they were still subordinated to the main/decisive strategic objective determined by the Stavka.
Each of the operations along the front would have secondary strategic goals, and one of those operations would usually be aimed towards the primary objective.
The strategic objective, or mission, was to secure the primary strategic target. The primary target usually consisted of a geographical objective and the destruction of a proportion of the enemy armed forces. Usually the strategic missions of each operation were carried out by a Soviet front. The front itself usually had several shock armies attached to it, which were to converge on the target and encircle or assault it. The means of securing it was the job of the division and its tactical components, which Soviet deep battle termed the tactical mission.

Terminology, force allocation and mission: The concept of deep battle was not just offensive. The theory took into account all forms of warfare and decided both the offensive and defensive should be studied and incorporated into deep battle. The defensive phase of deep battle involved identifying crucial strategic targets and securing them against attack from all directions. As with the offensive methods of deep battle, the target area would be identified and dissected into operational and tactical zones. In defence, the tactical zones, forward of the objective would be fortified with artillery and infantry forces. The outer and forwardmost defences would be heavily mined, making a very strong static defence position. The tactical zones would have several defence lines, one after the other, usually 12 kilometres from the main objective. In the zone 1–3 km from the main objective, shock forces, which contained the bulk of the Soviet combat formations, would be positioned.
The goal of the defence in depth concept was to blunt the elite enemy forces, which would be first to breach the Soviet lines, several times, causing them to exhaust themselves. Once the enemy had become bogged down in Soviet defences, the operational reserves came into play. Being positioned behind the tactical zones, the fresh mobile forces consisting of mechanized infantry, foot infantry, armored forces, and powerful tactical air support would engage the worn down enemy in a counter-offensive and either destroy it by attacking its flank or drive it out of the Soviet tactical zone and into enemyheld territory as far as possible.

Tukhachevsky's legacy: There are three standard doctrines about the military that help understand deep battle, as adopted by the US Army and the US Marine Corps:
1. Tactic
The lowest level is tactical, an aspect of individual skill and organization size.
2. Strategy
The highest level, an aspect of theater operation and the leadership of organization and of a government.
3. Operational
Operational is the bridge between tactics and strategy.
According to Colonel McPadden (US Army), the most precious legacy of Tukhachevsky is his concepts about all operations theory including the "operational art". Tukhachevsky is the first who used 'operational' as a systematic concept. According to McPadden, the main skill of a military commander is dependent on Tukhachevsky's theory, which is the ability to integrate tactics and strategy. This involves the capability of a commander on "the use of military forces to achieve strategic goals through the design, organization, integration and conduct of theater strategies, campaigns, major operations and battles."

Isserson; the factor of depth: Georgii Samoilovich Isserson (1898–1976) was a prolific writer on military tactics and operations.