The German Army was limited to four thousand officers per the Versailles treaty, and Guderian was one of the few who retained their commission. Initially, he served on the central staff of the Eastern Frontier Guard Service, who nominally defended Germany’s eastern border, before joining the Freikorps Iron Division as its second staff officer.
Intended to protect Germany from forces engaged in the Russian Civil War, this division waged an intense and brutal campaign against Bolsheviks that stretched through Poland, Lithuania, and into Lativia. Guderian used this time to develop his theories for mobile tactics, and in 1922 he was appointed the Army’s Inspector of Motorized Troops, a promotion that cemented his career within mechanized warfare.
Guderian rose through the ranks steadily, promoted to major 1927, when appointed to the Army’s command of transport and motorized tactics at Berlin, Lieutenant Colonel in 1931, and Colonel in 1933. He developed a reputation as a radical thinker, but many superior officers were uneasy with his transformative ideas.
Guderian’s bold, almost brash, tactics, tendency to alienate anyone who disagreed with him, and perennial habit of arguing with senior officers, generated a solid core of resistance against his ideas.
Frustrated, Guderian resorted to publishing his theories, which established his credentials as an eminent theorist in mechanized warfare, and he carefully followed his foreign counter-parts in France, Great Britain and the United States. Technology was evolving quickly, and Guderian began to envision a doctrine that emphasized coordinated, rapid movement between a powerful tank corps, mechanized infantry, and, increasingly, aircraft. The burgeoning potential of air power was not lost on the theorist.
Guderian’s promotions coincided with the rise of Adolf Hitler, and Germany’s massive rearmament program created an opportunity to bring the theorist’s concepts into reality. Guderian wrote a book entitled Achtung – Panzer! that laid out his theories, described the implications of a massive tank force, emphasized the importance of Germany’s rearmament… and caught the eye of the Fuhrer. His progress into the army’s highest ranks increased immediately, and on February 4, 1938, he was assigned command of the XVI Army Corps and promoted to Lieutenant General.
The newly promoted general could not have asked for a more powerful advocate, and Guderian’s theories appealed to Hitler’s desire for conquest, slaking the Fuhrer’s thirst by insisting on forward movement, outflanking prepared positions through mobility, and denying the enemy a chance to regroup. Guderian’s newfound connection with Hitler was not enough to overcome the resistance against his ideas, and when Nazi Germany smashed into Poland, he hoped to prove his theories on the battlefield.
Guderian commanded the XIX Corps during the invasion. Comprised of one panzer division and two motorized infantry divisions, the corps was capable of fighting the mobile war he envisioned, but the Poles lack of mechanized forces and outdated defenses did not allow Guderian to truly test his ideas. The upcoming invasion of France, however, was another matter.
Germany’s original plan to invade France satisfied no one. Known as Aufmarschanweisung N°1, Fall Gelb, the plan was a repeat of Germany’s WW I invasion strategy, and called for attacking the Allies through central Belgium. Lieutenant General Eric von Manstein hated the plan, decided the situation called for radical thinking, and quietly reached out to Guderian. Manstein knew the high command would reject any plan associated with the argumentative Guderian, and worked with him in secret.
Manstein was not disappointed. Guderian proposed avoiding the main body of the Allied armies by launching a blistering mechanized assault through the Ardennes forests to surprise the enemy, cut their supply lines, and isolate them against the English Channel. The plan was audacious and risky, and Guderian’s role in developing the strategy remained hidden until personally approved by Hitler.