During the winter of 1917-18 it was "quiet" on the Western Front—British casualties averaged "only" 3,000 a week. Serious attacks were impossible in the winter because of the deep caramel-thick mud. Quietly the Germans brought in their best soldiers from the eastern front, selected elite storm troops, and trained them all winter in the new tactics. With stopwatch timing, the German artillery would lay down a sudden, fearsome barrage just ahead of its advancing infantry. Moving in small units, firing light machine guns, the storm troopers would bypass enemy strongpoints, and head directly for critical bridges, command posts, supply dumps and, above all, artillery batteries. By cutting enemy communications they would paralyze response in the critical first half hour. By silencing the artillery they would break the enemy's firepower. Rigid schedules sent in two more waves of infantry to mop up the strong points that had been bypassed. The shock troops frightened and disoriented the first line of defenders, who would flee in panic. In one instance an easy-going Allied regiment broke and fled; reinforcements rushed in on bicycles. The panicky men seized the bikes and beat an even faster retreat. The stormtrooper tactics provided mobility, but not increased firepower. Eventually—in 1939 and 1940—the formula would be perfected with the aid of dive bombers and tanks, but in 1918 the Germans lacked both.