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Inter war

In the years following World War I, two of the technologies that had been introduced during that conflict, the aircraft and the tank, became the subject of strategic study.

The leading theorist of air power was Italian general Giulio Douhet, who believed that future wars would be won or lost in the air. The air force would carry the offensive, and the role of the ground forces would be defensive only. Douhet's doctrine of strategic bombing meant striking at the enemy's heartland—his cities, industry and communications. Air power would thereby reduce his willingness and capacity to fight. At this time the idea of the aircraft carrier and its capabilities also started to change thinking in those countries with large fleets, but nowhere as much as in Japan. The UK and US seem to have seen the carrier as a defensive weapon, and their designs mirrored this; the Japanese Imperial Navy seem to have developed a new offensive strategy based on the power projection these made possible.

British general J. F. C. Fuller, architect of the first great tank battle at Cambrai, and his contemporary, B. H. Liddell Hart, were amongst the most prominent advocates of mechanization and motorization of the army in Britain. In Germany, study groups were set up by Hans von Seeckt, commander of the Reichswehr Truppenamt, for 57 areas of strategy and tactics to learn from World War I and to adapt strategy to avoid the stalemate and then defeat they had suffered. All seem to have seen the strategic shock value of mobility and the new possibilities made possible by motorised forces. Both saw that the armoured fighting vehicle demonstrated firepower, mobility and protection. The Germans seem to have seen more clearly the need to make all branches of the Army as mobile as possible to maximise the results of this strategy. It would negate the static defences of the trench and machine gun and restore the strategic principles of manoeuvre and offense.

The innovative German Major (later General) Heinz Guderian developed the motorised part of this strategy as the head of one of the Truppenamt groups and may have incorporated Fuller's and Liddell Hart's ideas to amplify the groundbreaking Blitzkrieg effect that was seen used by Germany against Poland in 1939 and later against France in 1940. France, still committed to stationary World War I strategies, was completely surprised and summarily overwhelmed by Germany's mobile combined arms doctrine and Guderian's Panzer Corps.

Technological change had an enormous effect on strategy, but little effect on leadership. The use of telegraph and later radio, along with improved transport, enabled the rapid movement of large numbers of men. One of Germany's key enablers in mobile warfare was the use of radios, where these were put into every tank. However, the number of men that one officer could effectively control had, if anything, declined. The increases in the size of the armies led to an increase in the number of officers. Although the officer ranks in the US Army did swell, in the German army the ratio of officers to total men remained steady.