Defense Secretary Pete Hegseth is focused on a new enemy as the war with Iran rages on: the flu shot. Despite Hegseth's assertion that the flu vaccine mandate is "absurd," the military has a longstanding history of requiring vaccines dating back to nearly the country's inception. In 1777, General George Washington required troops to vaccinate themselves against smallpox. It was also the U.S. Army that invested in the development of the first flu vaccine at the start of World War II out of concern because the 1918 influenza pandemic killed about 45,000 to 50,000 U.S. soldiers during World War I. The flu vaccine was then mandated for all military personnel in 1945, until Hegseth's new announcement.