 Complete the following phrase:  The Germans used specially-trained stormtroopers to great effect in 1918, during Operation Michael, breaching the Allied trench lines and allowing supporting infantry to pour through a wide breach in the front lines. Even though most of the German forces were on foot, they were soon threatening Paris. Only timely and stiff resistance, the use of reserves, and German logistical and manpower problems prevented an Allied disaster. After this spring offensive, the Allies launched a 