Rear Adm. Robert Gilbeau enters the federal courthouse in San Diego on June 9. (Lenny Ignelzi/AP)

The highest-ranking officer convicted so far in a colossal Navy corruption scandal began accepting a cornucopia of gifts and prostitutes from an Asian defense contractor 20 years ago and later suffered a mental breakdown when he learned authorities were making arrests in the case, new court documents allege.

Robert J. Gilbeau became the first active-duty Navy admiral ever to be convicted of a felony when he pleaded guilty last year to lying to federal investigators. He is scheduled to be sentenced next month and likely faces up to 18 months in prison.

In a plea deal last June, Gilbeau admitted to making false statements about his contacts with Leonard Glenn Francis, also known as “Fat Leonard,” a crooked defense contractor from Singapore who has pleaded guilty to bribing scores of Navy officials. At the time, Gilbeau and federal authorities revealed little about the nature and extent of his relationship with Francis.

But in documents filed last week in federal court in San Diego, prosecutors allege that Gilbeau, 56, became corrupted in 1997 when he and another Navy officer met Francis during a port visit to the Indonesian island of Bali and succumbed to the contractor’s offer of free hotel rooms, lavish dinners and paid sex.

The relationship continued on a sporadic basis until 2012, according to prosecutors, who said Francis treated Gilbeau to numerous evenings at karaoke bars and luxury restaurants in Singapore, often capped off by assignations with prostitutes.

Rear Adm. Robert J. Gilbeau. (U.S. Navy)

Prosecutors allege that Gilbeau also pocketed $40,000 in cash bribes from Francis as part of a kickback scheme to overcharge the Navy for pumping wastewater from its ships.

The revelations show the origins and scope of the scandal — already the biggest in Navy history — stretch back seven years earlier than previously known. In cases against two dozen other defendants, prosecutors have focused on wrongdoing that began in 2004 and lasted until Francis’s arrest in 2013.

Authorities said last year that more than 200 people, including 30 admirals, were under investigation for potential crimes or ethical violations. The new evidence suggests that the roster of suspects has expanded and raises questions about how far into the past authorities will reach to hold people accountable.

Francis, who is being held in San Diego while he awaits sentencing, has admitted to gouging the Navy out of $35 million to resupply its ships in Asia. Investigators suspect that the total may have been far greater. His firm, Glenn Defense Marine Asia, did business with the Navy for a quarter century.

In court documents, Gilbeau and his attorneys said some of his actions were influenced by injuries he suffered during a mortar attack in Baghdad in 2007. He was awarded the Purple Heart. His doctors said he later developed severe depression and post-traumatic stress.

The explosion left him with shrapnel in his knee, back trauma, loss of hearing in one ear and a traumatic brain injury.

Prosecutors suggested that Gilbeau is exaggerating his condition. They said he began exhibiting overt symptoms of mental illness only in 2013 — right after news spread that Francis and several Navy officials had been arrested on corruption charges.

At the time, Gilbeau held a key command job in Afghanistan overseeing the logistical withdrawal of U.S. troops. When Francis’s arrest became public, Gilbeau began acting irrationally, showed signs of paranoia and became suicidal, according to his medical records.

Prosecutors said he suddenly made “ponderous, unsolicited remarks regarding Francis, dinners, and women” to colleagues in the war zone and asked for help in erasing data from his electronic devices. Military officials seized his sidearm and evacuated him to a hospital in Germany for observation.

While Gilbeau’s doctors said his behavior could be traced to the mortar attack injuries he had suffered in Iraq six years earlier, prosecutors argued that it stemmed from his “regret over being caught.”

Gilbeau has been receiving intensive psychiatric treatment ever since, according to medical records filed by his attorneys.

To ease his anxiety, doctors prescribed a therapy dog, a fluffy white Cavachon crossbreed named Bella. The 16-pound pooch, sporting a tiny Navy sweater, has accompanied Gilbeau into the courtroom for hearings.

In a letter to U.S. District Court Judge Janis Sammartino, who will sentence him next month, Gilbeau called himself “a broken and ashamed man” and said he was “deeply sorry” for making false statements to investigators. He did not address the allegations that he took bribes or prostitutes.

“I always thought I was on the right side of the law and drove the best deals for our Navy and the Department of Defense,” he wrote. “I apologize to the Navy, to my family and to this nation for the fact that my actions caused great damage to the Navy’s reputation.”

Under the terms of his plea deal, Gilbeau has agreed to pay $150,000 in fines and restitution. Prosecutors are pressing for an 18-month prison sentence.

In court papers, Gilbeau’s attorneys say he should be spared any time behind bars. His lead attorney, David Benowitz, declined to comment.

The Navy allowed Gilbeau to retire in October after 33 years of service, but it reduced him in rank from rear admiral to captain. It also discharged him under “less than honorable” conditions.

He is now receiving a military pension of about $111,000 a year. But in court papers, his attorneys argued that the demotion has cost him dearly. If he had been allowed to retain the rank of a one-star admiral, he would be entitled to an extra $692,000 in pension payments over 40 years.

Gilbeau also forfeited up to $2.4 million in disability benefits that the Department of Veterans Affairs would have had to pay him over the next four decades, according to his attorneys. His less-than-honorable discharge from the Navy rendered him ineligible.

According to court papers filed by prosecutors, Gilbeau was a supply officer assigned to the USS Boxer, an amphibious assault ship, when he met Francis in 1997. The documents state that Francis “plied Gilbeau and another U.S. Navy Officer with hotel rooms, dinners and the services of prostitutes” during a multi-day port visit to Bali.

The trio met again six years later when Gilbeau and his friend were serving on the USS Nimitz, an aircraft carrier. During a port call to Singapore in September 2003, Francis took Gilbeau and the other officer out to a nightclub with prostitutes, according to prosecutors.

Francis planned to follow the Nimitz to its next stop in Hong Kong, where he promised to entertain the two officers again. “Looking forward to some major engagement in HK bachelors pad,” he wrote them in an email.

Instead, after a last-minute schedule change, the Nimitz returned to Singapore. In an email to Francis, Gilbeau asked whether the contractor could arrange to take the two officers back to the same nightclub. His friend, he explained, wanted to see a “handball player” they had met during their last time in Singapore — a woman whom prosecutors described as “a particularly memorable prostitute.”

Francis enthusiastically agreed. “The Kahuna above has heard our prayers, will be standin by to Welcome you all back home to Papa Leonard soon,” he emailed. “The handball player is waiting eagerly to play.”

During the same 2003 port visit, prosecutors allege, Francis and Gilbeau conspired to overcharge the Navy for services provided to the Nimitz. Invoices show that Francis’s firm billed the Navy for pumping about 450,000 gallons of sewage and wastewater from the Nimitz over four days at about triple the usual amount.

Prosecutors contend that in exchange for approving the invoices, Gilbeau accepted about $40,000 in cash kickbacks from Francis. (Gilbeau has previously denied receiving money from the contractor.)

Their relationship resumed in 2005 when Gilbeau returned to Singapore to help coordinate the Navy’s tsunami relief efforts in the region.

Prosecutors allege that Gilbeau, who dubbed himself “Tsunami Bob,” went to dinner with Francis and partied with him at karaoke bars on three or four occasions. In addition, they allege that Francis, who called Gilbeau “Crazy Bob” or “Casanova,” paid for him to stay at the Singapore Marriott and other hotels several times.

Francis provided prostitutes to dozens of Navy officials over the years and kept meticulous notes about the sailors’ physical desires so he could cater to them, according to court records and interviews with people familiar with his methods.

In Gilbeau’s case, the defense contractor knew that the admiral liked to have sex with Vietnamese women — two at a time — so he supplied him with pairs of prostitutes on at least three occasions, according to prosecutors.

For example, in December 2010, Francis took Gilbeau out for dinner, drinks and karaoke in Singapore — and then paid for him to spend the night in a hotel suite with two prostitutes, prosecutors allege.

The next day, the defense contractor emailed the admiral to ask how the evening had gone.

“Very nice,” Gilbeau replied.

Tony Perry in San Diego contributed to this report.