In May 1970, Cairns, as chair of the Vietnam Moratorium Campaign, led an estimated 100,000 people in a "sit-down" demonstration in the streets of Melbourne. This was the largest protest in Australia until it was overtaken by the anti-Iraq war protests in February 2003. Similar protests of proportionate size took place simultaneously in other Australian cities. The predicted violence did not occur and the moral force of the, mainly young, protesters had a major effect on Australian attitudes to the war.