midnight
But on the eighth day a veritable fury launched itself upon that section of the American-French front , in the shape of seemingly endless brigades of Boches that were hurled `` over the top '' of their own breastworks , across No Man 's Land , and upon the first-line trenches of the Allies . For several days the American and French aviators had been reporting heavy German formations in that region , evidently with the design of a terrific assault , but the allied commanders had not expected it so soon , and in truth they were not fully prepared for it . It was a surprise attack in every sense of the word , with all the terrible carnage that such a battle brings . Shortly before midnight of the preceding night a terrible bombardment had been directed against the American-French trenches , and their hidden artillery to the rear of them . This was kept up for about seven hours , and the duel of heavy guns shook the earth like a quake and was deafening . Then , just as dawn was breaking , the infantry onslaught , participated in at some points by detachments of cavalry , began . For three hours the Americans and the French fought stubbornly and with every ounce of strength and determination .