Possibly originating with the Quakers, it was adopted by Africans, Indians, and U.S. civil-rights and anti-Vietnam War protesters. Among its most articulate advocates have been Gandhi, who maintained that action needs to be accompanied by love and a willingness to search for the truth, and Martin Luther King, Jr., who called for "tough-mindedness and tenderheartedness." Two of the most massive examples of passive resistance were the Solidarity movement in Poland (1980-81) and the Velvet Revolution in Czechoslovakia (1989). Opponents of passive resistance as a means of forcing a change in policy have criticized it for potentially fostering a general disrespect for law that could result in anarchy.