Tankman is the protestor who is unknown but his appearance during the Tiananmen Square Massacre actually is very famous. Many people would recognize the scene of the Tankman standing in front of a line of tanks and causing them to try to move around the man. In many ways it is probably the most popular image to anyone around the world in the late 20th century. This shows that one person can have the power during such a horrible situation.
It seems that in this case the tanks should win because they are loaded with guns and such destruction, but the brave Tankman stands in front of the tanks without letting them get by. It certainly defines the geopolitical situation during the previous century.