 By the end of the first day of what would be a months-long offensive, the Germans had pushed more than four miles through the British and were still advancing. In their wake, they left the bodies of an untold number of defenders, thousands of wounded and 21,000 prisoners. By March 23rd, three huge guns made by the arms manufacturer Krupp had been hauled forward and began sending shells into Paris, 72 miles away. 200 Parisians would be killed on that day alone.