Model spent the first year of World War II as a chief of staff, first of IV Corps during the invasion of Poland, and then of Sixteenth Army during the Battle of France.
He was promoted to lieutenant general (Generalleutnant) in April 1940, and earned his first senior command posting in November that year, when he was assigned to lead the 3rd Panzer Division.
He immediately proceeded to ignore all formalities of organization and command, which endeared him to his men and exasperated his staff—who often had to clean up the mess he left behind.

He also instituted a combined arms training programme where his men were thrown together in various ad-hoc groupings regardless of their parent unit: tankers would train with infantry, engineers with recon units, and so on.
Model thus anticipated by some months the regular German use of Kampfgruppen in World War II.
While this would become routine later on, it was still not a universal practice in the Wehrmacht in late 1940 and early 1941.
Model spent the first year of World War II as a chief of staff, first of IV Corps during the invasion of Poland, and then of Sixteenth Army during the Battle of France. He was promoted to lieutenant general (Generalleutnant) in April 1940, and earned his first senior command posting in November that year, when he was assigned to lead the 3rd Panzer Division. He immediately proceeded to ignore all formalities of organization and command, which endeared him to his men and exasperated his staff—who often had to clean up the mess he left behind.
He also instituted a combined arms training programme where his men were thrown together in various ad-hoc groupings regardless of their parent unit: tankers would train with infantry, engineers with recon units, and so on. Model thus anticipated by some months the regular German use of Kampfgruppen in World War II. While this would become routine later on, it was still not a universal practice in the Wehrmacht in late 1940 and early 1941.
Walter Model