Washington was not only fighting against the British. He was also fighting against an invisible enemy: smallpox.
Washington was quarantining his army who had the virus, but the British army wasn't as exposed to smallpox in Britain as much as Washington's army in America. They thought they were going to lose because everyone was getting sick. Washington initially said he was going to quarantine people and NOT inoculate them. But he changed his mind. Thanks to Rush, who wrote to Washington on February 13, 1777, on behalf of the Medical Committee, Washington decided to inoculate his soldiers.
But there were risks: if someone had smallpox, there was a 1 and 3 chance this soldier would die. If someone was inoculated and passed it along to other soldiers, his whole army would die.
But he took a chance, changed course, and took the risk in order to have the chance to fight for freedom.
Benjamin Rush's Challenging Friendship with George Washington