The one exception to this is that the historical scenario uses every single Stosstruppen counter available. But we all know that WWI was hard on the attacker, and the game reflects that. It will take the Germans the whole two weeks to push their way across the board. One quirk is that the Germans do not have a lot of troops where the British are weakest, in the south next to the French. So the greatest breakthroughs take place there, but there are often not enough units to exploit the success.
Variants allow free set-up.
The German advance is controlled by the management of supply. Some supply units will be dragged along to provide artillery support. Normally it is best for the Allied player to have an even spread of artillery support behind his whole line. Occasionally, however, there will be such a bad break in his line that he may have to put a supply unit into the breach. Normally this should be avoided, since they will fight with only a factor of 1, and they cannot be replaced if eliminated in combat.