Of the countless history books, TV documentaries and feature films made about World War II, many accept a similar narrative of the war in the West: Though Nazi Germany possessed a superior army, better equipment and by far the best weapons at the outset, the British somehow managed to hold on until the U.S. entered the war early in 1942. After that, with Germany seriously weakened by its brutal clash with the Soviet Union in the East, U.S. economic strength propelled the Allies to victory.

But according to James Holland, author of the three-volume history The War in the West, when it came to the operational level of World War II—the nuts and bolts of producing weapons, supplying troops and other logistics–the famous Nazi war “machine” was anything but efficient. It wasn’t even really a machine.

“Everyone always talks about the ‘Nazi war machine’ as though it’s entirely mechanized,” Holland told HISTORY. “Well it isn’t. Of the 135 divisions used in May 1940 for Blitzkrieg in the West, only 16 of those are mechanized. The other 119 are all using their own two feet, or they’re using horse and cart.”

In Holland’s view, the long-accepted wisdom of Germany’s military prowess relies too heavily on the experiences of individual Allied soldiers on the front lines, without taking into account the reality of the Wehrmacht’s logistical capabilities.

While understanding strategy (including leadership and overall war aims) and tactics (the actual fighting on the front lines) of any conflict is essential, he believes the operational level is what holds the strategic and tactical levels together.

“If you’re an American soldier and you’re in Normandy in a foxhole, and you come up against a Tiger tank, all you care about is that it’s a huge tank with a massive great gun and if it fires a shell at you, you’re going to be obliterated.”

Similarly, a Sherman tank facing off alone against one of the famously powerful German Tiger tanks would have no chance. “Looking at it operationally,” Holland explains, “a very different picture emerges. The Germans only built 1,347 Tiger tanks, whereas the Americans built 49,000 [Sherman tanks].”

And what about that Tiger tank? An icon of the Wehrmacht, the heavily armored monster featured a complex six-speed gearbox designed by Ferdinand Porsche. It was also prone to mechanical malfunction, difficult to sustain in combat and needed a lot of fuel, one of the many resources Germany sorely lacked.

Because Germany was so short on oil, steel and (most critically) food, Holland argues, the Nazis would have had to crush their enemies completely in the first phase of the war in order to have any chance of winning. Unable to defeat Britain in the West, Hitler had “absolutely no choice” but to invade the Soviet Union in the hopes of getting access to more resources. That invasion, of course, led to another enormously costly war for Germany on the Eastern Front, even as the United States joined Britain in the West.

Volume 1 of Holland’s planned trilogy was published in 2015. Volume 2, which focuses on the years 1941-1943, including the American entry into the conflict, debuts in the United Kingdom this week, and will be published in the United States in the fall.