Blitzkrieg
In 1939–1940, 45 percent of the army was 40 years old and 50 percent of the soldiers had only a few weeks' training. The German Army, contrary to the blitzkrieg legend, was not fully motorized and had only 120,000 vehicles, compared to the 300,000 of the French Army. The British also had an "enviable" contingent of motorized forces. Thus, "the image of the German 'Blitzkrieg' army is a figment of propaganda imagination". During the First World War, the German army used 1.4 million horses for transport and in the Second World War 2.7 million horses. Only ten percent of the army was motorized in 1940.
Half of the German divisions available in 1940 were combat ready, but they were less well-equipped than the British and French or the Imperial German Army of 1914. In the spring of 1940, the German army was semi-modern in which a small number of well-equipped and "elite" divisions were offset by many second and third rate divisions". In 2003, John Mosier wrote that while the French soldiers in 1940 were better trained than German soldiers, as were the Americans later and that the German Army was the least mechanized of the major armies, its leadership cadres were larger and better and that the high standard of leadership was the main reason for the successes of the German army in World War II, as it had been in World War I.

Luftwaffe: James Corum wrote that it was a myth that the Luftwaffe had a doctrine of terror bombing in which civilians were attacked to break the will or aid the collapse of an enemy by the Luftwaffe in blitzkrieg operations. After the bombing of Guernica in 1937 and the Rotterdam Blitz in 1940, it was commonly assumed that terror bombing was a part of Luftwaffe doctrine. During the interwar period, the Luftwaffe leadership rejected the concept of terror bombing in favour of battlefield support and interdiction operations:

The vital industries and transportation centers that would be targeted for shutdown were valid military targets. Civilians were not to be targeted directly, but the breakdown of production would affect their morale and will to fight. German legal scholars of the 1930s carefully worked out guidelines for what type of bombing was permissible under international law. While direct attacks against civilians were ruled out as "terror bombing", the concept of the attacking the vital war industries – and probable heavy civilian casualties and breakdown of civilian morale – was ruled as acceptable.
Corum continued: General Walther Wever compiled a doctrine known as The Conduct of the Aerial War. This document, which the Luftwaffe adopted, rejected Giulio Douhet's theory of terror bombing. Terror bombing was deemed to be "counter-productive", increasing rather than destroying the enemy's will to resist. Such bombing campaigns were regarded as diversion from the Luftwaffe's main operations; destruction of the enemy armed forces. The bombings of Guernica, Rotterdam and Warsaw were tactical missions in support of military operations and were not intended as strategic terror attacks.
J. P. Harris wrote that most Luftwaffe leaders from Goering through the general staff believed, as did their counterparts in Britain and the United States, that strategic bombing was the chief mission of the air force and that given such a role, the Luftwaffe would win the next war and that

Nearly all lectures concerned the strategic uses of airpower; virtually none discussed tactical co-operation with the Army. Similarly in the military journals, emphasis centred on 'strategic' bombing. The prestigious Militärwissenschaftliche Rundschau, the War Ministry's journal, which was founded in 1936, published a number of theoretical pieces on future developments in air warfare. Nearly all discussed the use of strategic airpower, some emphasising that aspect of air warfare to the exclusion of others. One author commented that European military powers were increasingly making the bomber force the heart of their airpower. The manoeuvrability and technical capability of the next generation of bombers would be 'as unstoppable as the flight of a shell.
The Luftwaffe ended up with an air force consisting mainly of relatively short-range aircraft, but that does not prove that the German air force was solely interested in "tactical" bombing. It happened because the German aircraft industry lacked the experience to build a long-range bomber fleet quickly and because Hitler was insistent on the very rapid creation of a numerically large force. It is also significant that Germany's position in the centre of Europe to a large extent obviated the need to make a clear distinction between bombers suitable only for "tactical" purposes and those necessary for strategic purposes in the early stages of a likely future war.

Fuller and Liddell Hart: The British theorists John Frederick Charles Fuller and Captain Basil Henry Liddell Hart have often been associated with the development of blitzkrieg, but that is a matter of controversy. In recent years historians have uncovered that Liddell Hart distorted and falsified facts to make it appear as if his ideas has been adopted. After the war Liddell Hart imposed his own perceptions after the event by claiming that the mobile tank warfare has been practiced by the Wehrmacht was a result of his influence. By manipulation and contrivance, Liddell Hart distorted the actual circumstances of the blitzkrieg formation, and he obscured its origins. By his indoctrinated idealization of an ostentatious concept, he reinforced the myth of blitzkrieg. Imposing retrospectively his own perceptions of mobile warfare upon the shallow concept of blitzkrieg, he "created a theoretical imbroglio that has taken 40 years to unravel". Blitzkrieg was not an official doctrine, and historians in recent times have come to the conclusion that it did not exist as such:

It was the opposite of a doctrine. Blitzkrieg consisted of an avalanche of actions that were sorted out less by design and more by success. In hindsight—and with some help from Liddell Hart—this torrent of action was squeezed into something it never was: an operational design.
The early 1950s literature transformed blitzkrieg into a historical military doctrine, which carried the signature of Liddell Hart and Guderian. The main evidence of Liddell Hart's deceit and "tendentious" report of history can be found in his letters to Erich von Manstein, Heinz Guderian, and the relatives and associates of Erwin Rommel. Liddell Hart, in letters to Guderian, "imposed his own fabricated version of blitzkrieg on the latter and compelled him to proclaim it as original formula". Kenneth Macksey found Liddell Hart's original letters to Guderian in the latter's papers. Liddell Hart requested Guderian to give him credit for "impressing him" with his ideas of armored warfare. When Liddell Hart was questioned about this in 1968 and the discrepancy between the English and German editions of Guderian's memoirs, "he gave a conveniently unhelpful though strictly truthful reply. ('There is nothing about the matter in my file of correspondence with Guderian himself except... that I thanked him... for what he said in that additional paragraph'.)".
During the First World War, Fuller had been a staff officer attached to the new tank corps. He developed Plan 1919 for massive independent tank operations, which he claimed were subsequently studied by the German military. It is variously argued that Fuller's wartime plans and post-war writings were inspirations or that his readership was low and German experiences during the war received more attention. The German view of themselves as the losers of the war may be linked to the senior and experienced officers' undertaking a thorough review in studying and rewriting of all of their Army doctrine and training manuals.
Fuller and Liddell Hart were "outsiders". Liddell Hart was unable to serve as a soldier after 1916 after being gassed on the Somme, and Fuller's abrasive personality resulted in his premature retirement in 1933. Their views had limited impact in the British army; the War Office permitted the formation of an Experimental Mechanized Force on 1 May 1927, composed of tanks, motorized infantry, self-propelled artillery and motorized engineers but the force was disbanded in 1928 on the grounds that it had served its purpose. A new experimental brigade was intended for the next year and became a permanent formation in 1933, during the cuts of the 1932/33–1934/35 financial years.

Continuity: It has been argued that blitzkrieg was not and that that the Germans did not invent something called blitzkrieg in the 1920s and 1930s. Rather, the German concept of wars of movement and concentrated force were seen in wars of Prussia and the German Wars of Unification. The first European general to introduce rapid movement, concentrated power and integrated military effort was Swedish King Gustavus Adolphus during the Thirty Years' War. The appearance of the aircraft and tank in the First World War, called an RMA, offered the German military a chance to get back to the traditional war of movement as practiced by Moltke the Elder. The so-called "blitzkrieg campaigns" of 1939 to around 1942 were well within that operational context.
At the outbreak of war, the German army had no radically new theory of war.