HIS father was killed by Croatian fascists during World War II, his daughter committed suicide last March, and today the world's most powerful military machine is focused on one thing: breaking his will. Bosnian Serb military commander Ratko Mladic is the key to ending a second round of NATO airstrikes, according to Western military officials. But the refusal by the indicted war criminal to remove his heavy weapons from around Sarajevo is threatening to scuttle last-ditch, US-sponsored peace talks in the region. ''Mladic personally is saying 'no' to withdrawing the heavy weapons from Sarajevo,'' says a senior Western military official. ''Mladic is clearly in control of what's going to happen and what's not going to happen.'' US officials say Serbian President Slobodan Milosevic and self-declared Bosnian Serb president Radovan Karadzic are urging General Mladic to withdraw the weapons. But he is refusing. Mladic's control of the Bosnian Serb army, which strongly backed him last month when Mr. Karadzic tried to oust him, remains unassailable. Western military officials say they are following a strategy of slowly increasing the pressure on Mladic and his war machine. The bombing of a communications relay tower in northern Bosnia on Tuesday reportedly cut Bosnian Serb communications with the outside world, but also may have cut off Mladic from his air-defense system and troops. Like the bombing campaign against Iraqi forces in the Gulf war, the slowly intensifying campaign in Bosnia is designed to ''blind'' Mladic. ''The level of pain is going to increase,'' says the Western military official. ''They can't move troops; they can't move ammunition; they can't move supplies.'' Mladic is known as a soldier's soldier. He sleeps and eats with the troops. He shows no signs of wavering - let alone breaking. In an interview aired Tuesday by Cable News Network, Mladic vowed never to succumb to Western pressure. He said this American bombing campaign would fail like campaigns in Vietnam did and that the West would flee Bosnia with its ''tail stuck between its legs.'' ''They cannot do anything to us,'' Mladic said in the CNN interview. ''The more they bombard us, the stronger we are.'' Mladic was born in southern Bosnia, an area he now refers to as ''old Herzegovina.'' Bosnia has never existed, according to Mladic and other Serb nationalists, who refuse to recognize it as a multiethnic nation. His father was killed by Croatian fascist soldiers fighting with Hitler in 1945. His daughter committed suicide last March 24 after reportedly becoming distraught over a newspaper article that called Mladic a ''sadist'' and accused him of being responsible for his army's war crimes. Mladic rose slowly through the old Yugoslav Army, making his mark during the disintegration of the former Yugoslavia. After Croatia broke away in 1991, Mladic won praise for his daring exploits and ruthlessness commanding rebel Serb forces. According to a published interview, Mladic said he carried Croat Army identification papers with him and frequently crossed the front lines. And he said he once defused a 70-pound explosive himself after engineers gave up on the task. In Bosnia, he has repeatedly defied the West. Last month, he oversaw the taking of the UN ''safe areas'' of Srebrenica and Zepa in southeastern Bosnia. Over 50,000 Muslims were then ''ethnically cleansed'' from the towns. Refugees describe Mladic as being kind while cameras were around and vicious in private. The UN war crimes tribunal indicted Mladic, along with Karadzic, as a war criminal last month. That means he is subject to arrest if he leaves Serb-controlled territory. But Western officials remain confident they can break him. ''Mladic has to be under tremendous pressure, but he's not showing it unless making bad decisions is a sign of it,'' says the Western military official. ''He should have withdrawn his weapons and gone for the demilitarization of Sarajevo. It was quite a mistake.''