SAN DIEGO — Over two decades, Robert Gilbeau rose through the ranks to Navy admiral and earned a chest-full of honors for his service, including a Bronze Star and Purple Heart. During that period he also partied across Southeast Asia with a gregarious Malaysian businessman who paid for lavish dinners, drinks at karaoke bars and prostitutes.

That businessman, known as “Fat Leonard,” is the centerpiece of a massive bribery scandal involving Navy officers, and Gilbeau last year pleaded guilty to lying to investigators about their relationship. He was the first active-duty admiral convicted of a federal crime and on Wednesday he learned his penalty: 18 months in jail.

Acting U.S. Attorney Alana W. Robinson called it a “somber day.”

“When tempted by parties and prostitutes, one of our most respected leaders chose karaoke over character, and cover-up over confession,” she said.

Gilbeau acknowledged his wrongdoing in federal court in San Diego. He told the judge he is “deeply sorry” and cannot explain his actions. He stood in court with his fluffy white dog, which accompanies him as part of his treatment for post-traumatic stress. Gilbeau’s defense had argued that his PTSD and a traumatic brain injury from a blast in Iraq should be taken into account, though prosecutors said he was exaggerating his condition because he knew he was going to get caught.

“I never wanted to end my career this way,” said the 56-year-old Navy veteran, who earned a Purple Heart and Bronze Star for his service in Iraq in 2007.

Gilbeau wrote in a letter to the judge that “I have no one to blame but myself.” He wrote that while his PTSD is not an excuse, it gave him a desire to “make self-destructive decisions.” Gilbeau was convicted in June after admitting he lied when he told federal agents he had never received any gifts from Leonard Glenn Francis. The Navy allowed him to retire in October but reduced his rank from rear admiral to captain.