British army chiefs began a major security review in Northern Ireland on Monday after the killing of eight soldiers, and Prime Minister Margaret Thatcher refused to rule out imprisonment without trial for rebel suspects. "We must never let the terrorists win," Thatcher told reporters during a visit to Plymouth. Asked if she planned a roundup of Irish Republican Army (IRA) guerrillas, she replied: "We are having a thorough review of all matters and nothing has been ruled out. You do not tell your enemy precisely what it is you're going to do, ever."