Arnhem, the Battle for the Bridges, by Antony Beevor, p. 10
There had been 4 million bicycles in the Netherlands at the beginning of the war, half as many as the total population. The Wehrmacht had commandeered 50,000 at the beginning of July 1942, and now thousands more were headed for Germany, most of them loaded with soldiers’ equipment and booty as they pushed them along the roads. With no rubber for tyres, pedaling them on wooden wheels was heavy work. But their loss hit hard.