In 1915, a German phosgene gas shell strayed from its target and hit a small village in France where Marie Curie's daughters were visiting a sick friend and were killed. Grief-stricken and seeking revenge, Curie proposed to the French government the idea of a dirty bomb to seed the enemy with radioactive material. A secret project began and two years later, several dirty bombs were dropped behind the Hindenburg Line in Northern France, killing thousands of soldiers with deadly amounts of radiation.