There are numerous meanings behind the clenched fist image, and the more modern is that of rebellion and militancy. This image has been used from around the early 1900s.
The clenched fist has been used as a symbol for many political parties and movements, including the United States Communist Party and the Black Panther Party for Self-Defense. The meaning changed somewhat when it was taken over by the New Left in 1968. It then became a representation of militancy and rebellion. The image took on a more simplistic appearance at this time. It has been popularly featured in a poster that was created in 1968 as a form of protest against the arrests of the Oakland Seven.