All for one, and one for all is a motto traditionally associated the King's Musketeers in the novel The Three Musketeers written by Alexandre Dumas. The motto has passed into popular usage as a statement of solidarity between comrades. It is used by the Hell's Angels, among others.
The original motto in the novel was actually: "One for all, and all for one." It was the motto of three musketeers (royal guards) who stayed loyal to the king of France in troubled times. The "one" probably meant the king and the "all" the people in the book.
