Also, in WW1 they were counting on the Russians being slow to mobilize. Massive armies are hard to get moving, after all. They were not only wrong on how long

Also, in WW1 they were counting on the Russians being slow to mobilize. Massive armies are hard to get moving, after all. They were not only wrong on how long it would take for the Russians to mobilize, they also overestimated their chances of knocking out France early.