The current pro-life movement is in part a continuation of previous debates on abortion that led to the practice being banned in all states in the late 19th century. The initial movement was led by physicians , but also included politicians and feminists . Among physicians, advances in medical knowledge played a significant role in influencing anti-abortion opinion. Quickening , which had previously been thought to be the point at which the soul entered a human was discovered to be a relatively unimportant step in fetal development, causing them to rethink their position of early term abortions.  Ideologically, the Hippocratic Oath and the medical mentality of that age to defend the value of human life as an absolute, also played a significant role in molding opinions about abortion. 
In a 2009 press release, Operation Rescue founder Randall Terry issued a statement calling for peaceful protests to expose abortionists. According to Media Matters and the Colorado Independent , however, Terry has also lead apparently contradictory public prayers that an abortion provider would "[convert] to God" or that "calamity [would] strike him".   Terry added that he hoped the "baby killer would be tried and executed for crimes against humanity".  The doctor targeted by Terry's prayers said to the press, "He's clearly inciting someone, anyone, to kill me."; a spokesman responded that Terry only meant that "God would deal with [the doctor]".