by Robin Knight TURNING POINTS. Events in Bosnia are a descent from "tragedy to catastrophe," says French President Francois Mitterrand. Bosnia now faces anarchy -- and the West may pull out. Last week, the third United Nations commander in six months was removed. Aid convoys ground to a halt. In Geneva, new peace talks collapsed. And in Britain, Canada, France and Spain, demands rose to withdraw U.N. troops. If another attempt to make peace, set for mid-February, fails, the entire U.N. operation is expected to be reviewed. For the West and the U.N., all this adds up to another turning point in a long string: April 1992. The United States and the European Community recognize Bosnia-Herzegovina. War begins. May 1992. Siege of Sarajevo begins. Of 380,000 people in the city at the start, 70,000 have left; 9,500 have been killed and 50,000 wounded. August-September 1992. London peace conference breaks up without an agreement. Later, U.N. forces deploy in Bosnia-Herzegovina, and a U.N. naval blockade begins. January 1993. Vance-Owen peace plan to divide Bosnia-Herzegovina into 10 cantons is unveiled. May 1993. After the U.N. proclaims a no-fly zone in April, Secretary of State Warren Christopher visits Europe but fails to forge a consensus. May 1993. Bosnian Serbs reject the Vance-Owen peace plan, which collapses in June. September 1993. The Bosnian parliament rejects the latest peace plan.