Blitzkrieg
The notion of a German blitzkrieg concept or doctrine survives in popular history and many historians still support the thesis.
Frieser wrote that after the failure of the Schlieffen Plan in 1914, the German army concluded that decisive battles were no longer possible in the changed conditions of the twentieth century. Frieser wrote that the Oberkommando der Wehrmacht (OKW), which was created in 1938 had intended to avoid the decisive battle concepts of its predecessors and planned for a long war of exhaustion (Ermattungskrieg). It was only after the improvised plan for the Battle of France in 1940 was unexpectedly successful that the German General Staff came to believe that Vernichtungskrieg was still feasible. German thinking reverted to the possibility of a quick and decisive war for the Balkan campaign and Operation Barbarossa.

Doctrine: Most academic historians regard the notion of blitzkrieg as military doctrine to be a myth. Shimon Naveh wrote, "The striking feature of the blitzkrieg concept is the complete absence of a coherent theory which should have served as the general cognitive basis for the actual conduct of operations". Naveh described it as an "ad hoc solution" to operational dangers, thrown together at the last moment. Overy disagreed with the idea that Hitler and the Nazi regime ever intended a blitzkrieg war because the once-popular belief that the Nazi state organized its economy to carry out its grand strategy in short campaigns was false. Hitler had intended for a rapid unlimited war to occur much later than 1939, but Germany's aggressive foreign policy forced the state into war before it was ready. The planning of Hitler and the Wehrmacht in the 1930s did not reflect a blitzkrieg method but the opposite. J. P. Harris wrote that the Wehrmacht never used the word, and it did not appear in German army or air force field manuals. The word was coined in September 1939 by a Times newspaper reporter. Harris also found no evidence that German military thinking developed a blitzkrieg mentality. Karl-Heinz Frieser and Adam Tooze reached similar conclusions to Overy and Naveh that the notions of blitzkrieg economy and strategy are myths. Frieser wrote that surviving German economists and General Staff officers denied that Germany went to war with a blitzkrieg strategy. Robert M. Citino argues:

Blitzkrieg was not a doctrine, or an operational scheme, or even a tactical system. In fact, it simply doesn't exist, at least not in the way we usually think it does. The Germans never used the term Blitzkrieg in any precise sense, and almost never used it outside of quotations. It simply meant a rapid and decisive victory (lightning war)... The Germans didn't invent anything new in the interwar period, but rather used new technologies like tanks and air and radio-controlled command to restore an old way of war that they still found to be valid, Bewegungskrieg.

Historian Victor Davis Hanson states that Blitzkrieg "played on the myth of German technological superiority and industrial dominance" and adds that German successes, particularly that of its Panzer divisions were "instead predicated on the poor preparation and morale of Germany's enemies". Hanson also reports that at a Munich public address in November 1941, Hitler had "disowned" the concept of Blitzkrieg by calling it an "idiotic word". Further, successful Blitzkrieg operations were predicated on superior numbers, air support and were possible for only short periods of time without sufficient supply lines. For all intents and purposes, Blitzkrieg ended at the Eastern Front once the German forces had given up Stalingrad, after they faced hundreds of new T-34 tanks, when the Luftwaffe became unable to assure air dominance, and after the stalemate at Kursk. To that end, Hanson concludes that German military success was not accompanied by the adequate provisioning of its troops with food and materiel far from the source of supply, which contributed to its ultimate failures. Despite its later disappointments as German troops extended their lines at too great a distance, the very specter of armored Blitzkrieg forces initially proved victorious against the Polish, Dutch, Belgian and French Armies early in the war.

Economics: In the 1960s, Alan Milward developed a theory of blitzkrieg economics: Germany could not fight a long war and chose to avoid comprehensive rearmament and armed in breadth to win quick victories. Milward described an economy positioned between a full war economy and a peacetime economy. The purpose of the blitzkrieg economy was to allow the German people to enjoy high living standards in the event of hostilities and avoid the economic hardships of the First World War.
Overy wrote that blitzkrieg as a "coherent military and economic concept has proven a difficult strategy to defend in light of the evidence". Milward's theory was contrary to Hitler's and German planners' intentions. The Germans, aware of the errors of the First World War, rejected the concept of organizing its economy to fight only a short war. Therefore, focus was given to the development of armament in depth for a long war, instead of armament in breadth for a short war. Hitler claimed that relying on surprise alone was "criminal" and that "we have to prepare for a long war along with surprise attack". During the winter of 1939–1940, Hitler demobilized many troops from the army to return as skilled workers to factories because the war would be decided by production, not a quick "Panzer operation".
In the 1930s, Hitler had ordered rearmament programs that cannot be considered limited. In November 1937, he had indicated that most of the armament projects would be completed by 1943–1945. The rearmament of the Kriegsmarine was to have been completed in 1949 and the Luftwaffe rearmament program was to have matured in 1942, with a force capable of strategic bombing with heavy bombers. The construction and the training of motorized forces and a full mobilization of the rail networks would not begin until 1943 and 1944, respectively. Hitler needed to avoid war until these projects were complete but his misjudgements in 1939 forced Germany into war before rearmament was complete.
After the war, Albert Speer claimed that the German economy achieved greater armaments output not because of diversions of capacity from civilian to military industry but by streamlining of the economy. Overy pointed out some 23 percent of German output was military by 1939. Between 1937 and 1939, 70 percent of investment capital went into the rubber, synthetic fuel, aircraft and shipbuilding industries. Hermann Göring had consistently stated that the task of the Four Year Plan was to rearm Germany for total war. Hitler's correspondence with his economists also reveals that his intent was to wage war in 1943–1945, when the resources of central Europe had been absorbed into Nazi Germany.
Living standards were not high in the late 1930s. Consumption of consumer goods had fallen from 71 percent in 1928 to 59 percent in 1938. The demands of the war economy reduced the amount of spending in non-military sectors to satisfy the demand for the armed forces. On 9 September, Göring, as Head of the Reich Defense Council, called for complete "employment" of living and fighting power of the national economy for the duration of the war. Overy presents that as evidence that a "blitzkrieg economy" did not exist.
Adam Tooze wrote that the German economy was being prepared for a long war. The expenditure for the war was extensive and put the economy under severe strain. The German leadership were concerned less with how to balance the civilian economy and the needs of civilian consumption but to figure out how to best prepare the economy for total war. Once war had begun, Hitler urged his economic experts to abandon caution and expend all available resources on the war effort, but the expansion plans only gradually gained momentum in 1941. Tooze wrote that the huge armament plans in the pre-war period did not indicate any clear-sighted blitzkrieg economy or strategy.

Heer: Frieser wrote that the Heer (German pronunciation: [ˈheːɐ̯]) was not ready for blitzkrieg at the start of the war. A blitzkrieg method called for a young, highly skilled mechanized army. 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.