The U.S. government became interested in penicillin after entering World War II. In previous wars, soldiers were more likely to die from infections that developed following wounds than from the wounds themselves. The government was anxious for anything that could reduce American casualties, and it made penicillin production a priority. The government's interest spurred more than 20 companies to join the efforts to produce sufficient quantities of penicillin. Production ramped up so much that by the invasion of Normandy in June 1944, companies were producing 100 billion units of penicillin per month.