LAS VEGAS >> Prosecutors began casting a former mixed martial arts fighter named War Machine on Monday as violent in his relationship with his porn star girlfriend and murderous when he found her asleep one morning with another man in her bedroom.

Jonathan Paul Koppenhaver’s defense attorney, Jay Leiderman, didn’t deny during opening statements that a fight took place early one morning in August 2014.

But he characterized Christy Mack and Koppenhaver as “two damaged people” — each with an adopted public name, deep image insecurities and a co-dependent relationship that revolved around sex, constant attention and internet personas that exploded into violence.

“It was a co-dependency that was bound to erupt at some time,” Leiderman told the state court jury during opening statements in a trial expected to last a couple of weeks.

Koppenhaver has pleaded not guilty to all 34 felony charges against him, including kidnapping, attempted murder and multiple counts of sexual assault that could get him life in prison without parole if he’s found guilty.

“The two of them were swallowed up by the personas they had created for themselves,” Leiderman said.

They met as performers on an adult film shoot. Koppenhaver legally changed his name to War Machine during his 19-fight MMA career, and he started a clothing line he called Alpha Male. She shortened her given name, Christine Mackinday, for her adult film career. She cheered ringside at his martial arts bouts. He became jealous of her professional sexual encounters.

The Associated Press usually doesn’t identify alleged victims of sexual assault, but Mack gave the AP permission to use her name. She is expected to testify during the trial.

Among their many tattoos, he has her name, “Mack,” tattooed in large letters across his throat. She had “Property of War Machine” inked in red on the back of her right shoulder.

Prosecutor Jacqueline Bluth told jurors that Mack liked to be choked during sex, sometimes to unconsciousness. Leiderman said Mack had rape fantasies, and invited Koppenhaver to surprise her.

Thomas, a digital media company owner who is both taller and heavier than Koppenhaver, testified Monday that he dated Mack for two months before Koppenhaver arrived unexpectedly, flipped on the bedroom lights and set upon him on the bed with rapid-fire punches and chokes that nearly left Thomas unconscious.

High school wrestling experience and a couple of years of unarmed defense training helped Thomas escape, he said, along with the presence of mind to ask Koppenhaver whether he was going to kill him or let him leave.

Thomas testified that he ended up with a broken nose, dislocated shoulder, scrapes and bruises, and bite marks on his face and arm. Koppenhaver let him go with a warning that if he went to the police, Koppenhaver would enlist friends who are Navy SEALs and Hells Angels bikers to hurt him, Thomas said.

Mack testified in 2014 that after Thomas left, Koppenhaver attacked her — leaving her with a broken nose, missing teeth, fractured eye socket, leg injuries and a lacerated liver.

She has said she drifted in and out of consciousness as she was beaten, kicked and groped sexually. She said she escaped when she thought Koppenhaver was in the kitchen fetching a knife to finish her off. She ran naked and bleeding to neighbors’ homes.

Koppenhaver, now 35, was arrested in the Los Angeles suburb of Simi Valley a week after the alleged attack in Las Vegas.

He has been in Nevada state custody since that time, serving 1½ to four years in prison after his probation was revoked for a prior conviction in a 2009 attempted battery causing substantial bodily harm case involving a 21-year-old woman.

Koppenhaver made his Ultimate Fighting Championship debut in 2007, and he had a 14-5 record as a welterweight. His final fight was in 2013.

He was dropped by his fight promoter and his clothing line after Mack’s accusations became public.

He told a judge in 2014 that he would use the name Koppenhaver in court.