LAURENCE REES: Let's start by talking about September 1939. To what extent was the German Army that invaded Poland a completely mechanised army?

GEOFFREY WAWRO: Well, the Germans were trying to overcome the principal problem in the First World War, which was the continuous expansion of mass. The armies got bigger and bigger, the fronts got longer and deeper and it was impossible to break through or turn a flank, and so the idea behind the whole Blitzkrieg concept, which the Germans called Bewegenskrieg, was to mobilise the army, mechanise it and make it a much sharper, faster instrument that could achieve breakthroughs or rapid flanking operations. That was the concept behind Blitzkreig. But in fact the German Army was very slightly mechanised. In Poland, in Norway, in France, and in Yugoslavia this was an army that had an armoured spearhead but the spear itself was largely foot marching and horse drawn. Eighty-five percent of the German Army in 1939 and still in 1944 is drawn by horses. In the invasion of France in 1940 only seven of the forty-five divisions in the critical army group A were armoured divisions. And so you get a sense of this armoured spearhead but then this big sort of foot marching, horse drawn mass behind it. And the reason the Germans were successful with Blitzkrieg was that they were facing - surprisingly - relatively unprepared and unschooled enemies that weren’t expecting the new rapid tempo.

There were armies like the French Army, fighting its methodical battle very much along the First World War lines, where you bring up the infantry, you concentrate the artillery and you have tanks distributed in small packets to support the infantry. The Germans have this idea of rapidly exploiting the mobility of tanks to sweep around flanks or achieve breakthroughs. But the critical flaw in Blitzkrieg was that it worked against relatively small, unprepared enemies in relatively confined theatres.

Blitzkrieg certainly didn’t work in a much larger war, like the invasion of the Soviet Union, where you needed to spread an armoured mass over a much bigger frontage and then eventually have to deal with an industrialised adversary who was also bulking up his armoured forces. The whole Blitzkrieg concept was also key in the German end to achieve a quick victory that would get Germany out of the war. Because Germany was never prepared for a long war, Hitler was always having to balance domestic constituencies against the demands of the German Army, and so he hesitated to fully mobilise Germany economically or fully embody all of Germany’s manpower resources into the Wehrmacht or the Luftwaffe or the German Navy. And so they had to win quickly and they did win these early campaigns, but they were never definitive; they never achieved an end to the war. The Germans remained in the war and then by attacking the Soviet Union and then eventually bringing in the United States it was game over, because in an attritional war of industrial production there was no hope the Germans were going to win.