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 series of counter-attacks with tanks and small units of assault infantry protected by air support and short intense artillery barrages while the main infantry force followed and seized strongpoints. This forced the Germans back and after less than three months the allies had made the largest territorial gains on the western front since the war began. The Germans then sued for peace ending the war.