The British seized Allen and held him on a series of prison ships, then moved him to England. As an officer of the Continental Army he would have been executed, but the British feared reprisals.
Allen was held for two years in England, then sent back to America as part of a prisoner exchange.
Abraham Lincoln loved to tell a story about what happened to Allen after the war. Though it may not be true, it's characteristic of Allen, who was controversial in life, brash, crude and daring.
He opposed organized religion and wrote an attack on Christianity called Reason: the Only Oracle of Man. He married a Loyalist only a few weeks after meeting her and only six months after his first wife died.
Ironically, Ethan Allen's daughter Fanny converted to Catholicism and became New England's first nun.
Here is the story as Lincoln liked to tell it.
Ethan Allen returned to England after the war, and the British made fun of him. One day they put a picture of George Washington in an outhouse where Allen would be sure to see it. He used the outhouse but said nothing about the picture. Then the British asked him about it and Allen said it was a very appropriate place for an Englishman to hang the picture because “nothing will make an Englishman shit so quick as the sight of General Washington.”
There is little evidence to support the truth of the story, though Lincoln most certainly told it.
This story was updated in 2017.