noon
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 . Whole regiments and even brigades were wiped out on both sides , but the Boches , who had prepared every detail of the assault for weeks , were readier than their opponents and filled the gaps in their lines more quickly . By noon it became apparent that the sacrifice of lives was becoming too great to warrant the Allies trying to hold their first-line trenches much longer , and that they must give them up , at least until they could re-mobilize their forces for a counter-attack . The order was therefore given for those in the rear , including food and ammunition trains , field hospitals , etc. , to fall back , in order to make way for the strategic retreat of those on the front when the moment for that retreat came . Everything moved like clockwork , and with the greatest possible speed . And throughout it all men on both sides were shooting , shouting , shrieking , fighting , falling , while others , trapped in their dug-outs , either surrendered or fought desperately on until they fell wounded or lifeless before superior numbers .