World War I is often viewed as a war fought by armies of millions living and fighting in trenches, aided by brutal machinery that cost the lives of many. But behind all of this an intellectual war was also being fought between engineers, chemists, code-breakers, physicists, doctors, mathematicians, and intelligence gatherers. This hidden war was to make a positive and lasting contribution to how war was conducted on land, at sea, and in the air, and most importantly, life at home.