Marvelous Marvin Hagler knew all about the new style of bobbing and weaving Mustafa Hamsho planned to bring into the ring tonight at Madison Square Garden. Hamsho was supposed to have refined his "LaMotta style," and keep his chin tucked into his chest, his fists unleashing flurries that would break the strength and will of the undisputed middleweight champion of the world.

And Hagler also knew about the ghost Hamsho claimed to carry around with him, the bright memory of Paddy Flood, his former trainer who died of a brain hemorrhage last year.

After Hamsho, the haunted one, had fought and lost to Hagler three years ago, he had promised Flood that there would be "a next time," and he would avenge the loss. That next time happened tonight before 16,000, and it ended with Hamsho on his back and beaten at 2:31 in the third round, his face a bloody mess. Hagler (60-2-2) won the technical knockout when referee Arthur Mercante stepped in and called the title fight after "the man's head was broken," as Hagler put it.

The end was stunning. Hagler connected with a brutal combination early in the third round that dropped Hamsho (38-3-2) to the canvas. As soon as the challenger came back for more, Hagler drilled him with punching-bag precision, rocking Hamsho around the ring. "I put punches together and meant to break his head," Hagler said. "Don't you know I have muscles in this head or skull or whatever it is?"

When Hamsho fell the second time, there was no doubt that he wouldn't come up again. He gazed into the screaming bank of overhead lights as blood dribbled down his cheek and wet the canvas. Hagler claimed such a finish was a perfect end for a fighter who fought "dirty and tried to get me with his head."

"The public seen it," Hagler said. "The referee saw it but he didn't do anything about it. I can't leave a fight up to the referee and the judges. The only way to do it is my own way.

"I told him after the first round: 'If you play dirty, I'll play dirty. I'll show you how to fight.' "

In the first round, Hagler and Hamsho met at center ring and the challenger came away with a small cut over his left eye. Hagler popped him later in the round and the blood began to pour. Hagler said he didn't think he had hit him hard enough to cut him. "He probably did it himself," he said.

But the blood obscured Hamsho's vision, but even full-sighted, Hagler would have been too strong. The last salvo that ended Hamsho was both brutal and beautiful, and when Hamsho fell, Hagler went first to a neutral corner, then came back to hold his hands high in victory. The collection of prize belts he held over his head was testament of his dominance in the middleweight class.

Hagler said he would like to fight Thomas Hearns, the junior middleweight champion, but that seemed unlikely, considering Hearns fights only "cripples and old men who can't walk . . . If you can get Thomas Hearns in the ring with me, I'll pay you. If he doesn't come and fight me, he'll be missing a good thing. I wanted the glory of fighting Sugar Ray Leonard, and now that that's gone, I figure the only chance for the really great fight would be with Hearns.

"I fought all oncomers and beat them (in 10 successful defenses). I don't want to back-step but move on. Everybody knows I'm the true champion. Thomas Hearns knows I'm the true champion."

Steve McCrory, the Olympic gold medalist, was successful in his professional debut, defeating "Gentleman" Jeff Hannah (11-6) with a technical knockout early in the fourth and final round. A left hook to the stomach, called "a liver punch" by McCrory's corner, leveled the Indinapolis fighter and left him gasping for breath, unable to rise from the canvas.

"I'm the hardest-hitting flyweight in the world," McCrory said afterward.

McCrory, a dynamo of speed and fury at 115 pounds, opened with a vicious flurry to the head of Hannah, who spent most of the fight hiding his face behind his red gloves. McCrory scored quickly with flashing right jabs to the jaw of his opponent and obviously intimidated the overmatched Hannah.

A hard combination in the second round stunned Hannah, who went flying into the ropes and nearly fell into the banks of reporters' tables at ringside. Hannah threw a few nice punches, but nothing with speed and power, and all were blocked by the quick McCrory.

Hannah came into the final round with a face a shade or two deeper than his gloves, and slid across the ropes looking for a place to hide from the relentless McCrory. But a left hook ended Hannah's will to continue and his knees buckled beneath him. When he fell, McCrory raised his gloves and hustled to his corner. It was easy, but it was victory.

In the first undercard bout, Ricky Womack (2-0) of Detroit's Kronk Boxing Team won a unanimous decision over Gerry Parker (2-1) in four rounds. Womack scored early with hard right jabs to the head and body of Parker, who was sent reeling in the middle of the second round. Womack spent the third and fourth rounds fighting off the desperate grasp of Parker. At one point, the referee stopped the bout and admonished both fighters for head-butting and using forearms.

Mike (The Body Snatcher) McCallum ran his record to 22-0 with a unanimous decision over Sean (War-Head) Mannion (29-6-1) in a bout for the World Boxing Association junior middleweight title. The 15-round fight saw Mannion, from Ireland, leave the ring beaten and bloodied, and McCallum climbing the corner ropes with his gloves held high in victory.

In the last few rounds, Mannion somehow managed to remain standing even while reeling under the barrage of blows thrown by McCallum, who appeared not even winded when he finally climbed down from center stage.