> in peacetime the German economy is already on a heavy war footing.

This is propaganda by the Allies before and after the war.

Recall that the Versailles Treaty crippled and excessively limited the German military in the 1920s. So the Germans did a lot of catching up in the 1930s and eagerly bragged about this in news films. In fact, much of the logistics in the invasion of Poland was via horses though we see the films of mechanized/tanks. Speer explained that there was a reluctance to fully mobilize in part because the German leadership was very sensitive to keeping consumer goods going to the public and in part because they thought they could negotiate from a position of strength after Poland -- not anticipating a full fledged scorched-earth unconditional-surrender war over a country far from the UK and France. While at a train station, Goebbels complained about seeing upper-class German women wearing furs riding in 1st class returning from vacations in Italy as late as 1943 while the soldiers being shipped out wait sitting on the cold concrete. That's when (plus considering the defeat in Stalingrad shocked everyone) he made his "Total War" speech and war production accelerated by Speer. Look at war production output charts comparing 1938 through 1944, and it is clear as night and day supporting my argument.