In addition, the majority of the senior officers and many of the middle-ranking officers were men that Seeckt had chosen to retain in the Reichswehr.[80] Seeckt created 57 different committees to study the last war to provide lessons learned for the next war.[80] Seeckt stated: "It is absolutely necessary to put the experience of the war in a broad light and collect this experience while the impressions won on the battlefield are still fresh and a major portion of the experienced officers are still in leading positions".[80] The result was the 1921 book Leadership and Battle with Combined Arms that outlined the combined arms tactics and operational ideas that went on to serve as the Wehrmacht's doctrine in the Second World War.[81][80] Seeckt envisioned Germany winning the next war by a series of highly mobile operations featuring combined arms operations of artillery, infantry, armor, and air power working together to concentrate superior firepower to crush the enemy at crucial points.[82][2] Seeing a significant role for air power in the next war, Seeckt kept a large number of officers in the Reichswehr who had experience in air combat.