Six men made major scientific breakthroughs during the First World War and in doing so altered its course. Lawrence Bragg pinpointed the position of enemy artillery pieces with sound ranging, which enabled British tanks to break through in late 1917 and 1918. His father worked with the French to develop high frequency echolocation; if the war had gone on longer sonar would have curbed the U-boats. Ernest Starling led a group that discovered the cause of wound shock and saved shocked men with artificial plasma. He utilized what was known about metabolism to ration food fairly in Britain while improving the poor’s nutrition. Germans starved. Otto Hahn worked on poisons for gas warfare and devised and tested filters to trap the poisons. He also became an expert on tactics for breaking through enemy lines with gas. Chaim Weizmann and other chemists produced molecules essential for making high explosives; German chemists enabled their side to keep in the war. Antiaircraft defense was developed by the physiologist A. V. Hill who led more than 100 scientists and mathematicians, who learned how to aim supersonic shells to explode near fast-moving targets. Now these threads are brought together for general readers, telling how some of the foremost scientists of all time used their remarkable talents for significant war research. The information comes from their memoirs, letters, reports in the archives, and from coworkers recollections. Four of these brilliant and diverting men were Nobel laureates and one became the president of Israel. The work of two outstanding women is described in the narrative.