Steven J. Zaloga 
US Field Artillery of World War II [PDF ebook] 

Determined to learn from the lessons of World War I, the US Army developed a new generation of field artillery weapons and tactics during the 1930s. Consequently, in World War II it was the clear leader in field artillery. Providing a thorough examination of the many critical innovations and doctrines, and the impact they had on performance, including the motorization of artillery, Fire Direction Centers, aerial observation, and radio communications. Exploring, in their entirety, the weapons that formed the backbone of the US artillery arsenal in World War II, this book reveals a wealth of detail not readily available elsewhere.