SAN DIEGO >> The laughter and chatter ceased as soon as the two naval chiefs appeared on the rooftop deck of the barracks, where four sailors — three men and one woman — were having drinks in a hot tub with a sweeping view of San Diego Bay.

Chief Petty Officer John Tate approached the group and asked a 23-year-old in a don’t-try-to-fool-me tone whether his Gatorade bottle was spiked. Then Tate turned to the only female in the hot tub: “You on the same ship? You drinking a little bit, too?”

“I’m just sipping on it,” she said.

There was no mention of the military’s push to prevent sexual assaults in its ranks, but those in the hot tub at Naval Base San Diego said they knew that’s why Tate was there. Tate serves on one of the Navy’s new nightly patrol units charged with policing bases to control heavy drinking and reckless behavior.

The patrols are among a number of new initiatives the armed forces is implementing to try to stop sexual assaults by changing the military’s work-hard, play-hard culture. The effort follows a Pentagon report, released in May, that estimates as many as 26,000 service members may have been sexually assaulted last year.

The head of the Army has called sexual assault “a cancer” that could destroy the force, while Defense Secretary Chuck Hagel said the problem threatens to undermine troops’ effectiveness in carrying out missions. But military leaders have rejected far-reaching congressional efforts to strip commanders of some authority in meting out justice, saying that would undercut the ability of commanders to discipline their troops.

Now every branch is scrambling to demonstrate it can get the situation under control by instituting new measures that emphasize a zero-tolerance message and crack down on alcohol, which is said to be a major contributor to the problem.

“We need cultural change, where every service member is treated with dignity and respect, where all allegations of inappropriate behavior are treated with seriousness, where victims’ privacy is protected, where bystanders are motivated to intervene, and where offenders know that they will be held accountable by strong and effective systems of justice,” Hagel said after the report was released.

Hagel ordered all commanders to inspect workspaces by July 1 to ensure they were free of degrading material, and he gave military leaders until Nov. 1 to recommend ways to hold officers accountable for their commands’ environments.

In June, thousands of military men and women attended interactive, in-your-face training programs as part of a Pentagon-ordered stand-down from regular duties to specifically address sexual assault. The service members role-played uncomfortable scenarios, watched explicit videos that included rape scenes and were grilled over the meaning of “consent” in boot camp-style lectures. Some branches allowed media to attend the sessions.

During one course at the Marine Corps Recruit Depot on Parris Island, S.C., 1st Sgt. Rena Bruno paced in front of screens filled with statistics as she schooled 200 recruits, in their 10th day of basic training, on the definitions of sexual assault and harassment.

“We’re tired of hearing about it in every military branch!” Bruno bellowed. “It brings dishonor to the Marine Corps! You got that?”

“Yes, ma’am!” the young men yelled back.

Bruno cited an incident in which a Marine drugged his roommate, and then videotaped the ensuing encounter. The class groaned, but recruit Alex Ritter, 21, of Lafayette, La., said Bruno’s message came through loud and clear: “It shows what’s happening both in the civilian world and in the armed forces.”

At another class at Eglin Air Force Base in the Florida Panhandle, about 200 airmen, mostly in their 20s, watched videos that showed an old World War II bomber plane decorated with a painting of a pinup girl and a sexually suggestive squadron patch.

Saying the culture has to change, Lt. Col. Rick Hughes told the group: “America’s view is that the military condones sexual assault.”

At Fort Bliss Army base in Texas, Sgt. Wallace Levy inappropriately rubbed a soldier’s back to see if those in his training class would react. When no one did, he admonished them: “Don’t look the other way if you see it happening.”

Each branch of the military is imposing new rules, mostly aimed at service members in their 20s, who the Pentagon says are most vulnerable to an attack.

The Army implemented a 9 p.m. curfew and banned alcohol for young soldiers at 22 of its basic training facilities. The Marine Corps’ top leader ordered “climate surveys” for all new commanders to check for harassment, hazing and alcohol problems among their subordinates.

The Air Force put a female two-star general in charge of a beefed-up office responsible for sexual assault prevention and response, while the U.S. Air Force Academy in Colorado hired a civilian psychology professor to teach courses on interpersonal violence and men and masculinity for one year.

The Navy plans to replicate the nightly patrols roaming San Diego’s bases at some 70 installations worldwide, including in Pensacola, Fla.; Naples, Italy; and Yokosuka, Japan.

Military officials are also learning from mistakes made while trying to address the problem. Responding to a lawmaker’s complaints, the Air Force this summer pulled a brochure circulated at a South Carolina base that stated, “If you’re attacked, it may be advisable to submit than to resist.”

Some service members have bristled at the new restrictions, calling them unfair for punishing all for the sins of a few.

“This represents the military’s simplistic approach to solving a complex issue that it has ignored for years,” Army Spc. Sam Ellison, a 28-year-old soldier at Texas’ Goodfellow Air Force Base, which has a 9 p.m. curfew for new troops, wrote in an email to the Army Times newspaper.

Ellison said the misguided thinking is, “If we treat all of the soldiers like criminals, they can’t commit crimes.”

“Big Brother would be proud,” he wrote.

Military officials defended the actions, given the rise in cases. The Pentagon report found a 6 percent increase in reported sexual assaults, or 3,374 cases, in fiscal year 2012 over the previous year. But officials believe the problem is far worse. Based on that number and anonymous surveys of service members, the Pentagon estimated the number of victims may be as high as 26,000.

More people are stepping forward after word spread about resources for victims, including a 24-hour hotline and expedited transfers from a unit after an abuse is reported. But the crime is still widely underreported because of fear of retaliation and other reasons, Pentagon officials said.

The Pentagon established its Sexual Assault Prevention and Response program eight years ago with the goal of reducing attacks through annual training and campaigns to encourage more reporting by victims. Since then, the number of reported cases has risen by 98 percent — which critics say shows the need for judicial reform.

“Until there are structural changes, you’re not going to train your way out of this epidemic,” said Brian Purchia of Protect Our Defenders, a nonprofit that helps military sexual assault victims. “There needs to be actual punishment.”

A sweeping defense bill approved by the U.S. House in June would impose new punishments, including requiring a mandatory minimum sentence of two years in prison for military personnel convicted of rape or sexual assault. The bill also would strip military commanders of the power to overturn convictions in those cases. The Senate is expected to take up the issue this fall.

Navy Lt. Cmdr. Nathan Christensen, a Pentagon spokesman, said Hagel has not ruled out any remedies but that “the key to preventing sexual assaults … will be our commanders” and the standards they set.

Troops also are being trained to speak out if a higher-ranking officer behaves inappropriately, military authorities said.

In San Diego, Chief Petty Officer Tate said the roving patrols, along with other measures, seem to be making a difference.

Six months ago, the Navy banned pitchers of beer at bowling alleys and pizza parlors on all three of its bases in the city. At the same time, each base also launched a resident adviser program. Chief petty officers now live in every barrack and are trained to respond to situations that could spiral out of control.

Many of the resident advisers, like Tate, also serve on the roving patrols, which started in February and were modeled after a similar effort at the Navy’s training facility for new recruits in Great Lakes, Ill. Sexual assaults there dropped by more than 60 percent over a two-year period.

In San Diego, rotating teams of two senior enlisted officers patrol from 7 p.m. to midnight on weekdays and from 11 p.m. to 5 a.m. on weekends, walking from barrack to barrack to peek in on communal areas before checking popular drinking spots.

On a warm May night at Naval Base San Diego, Tate and his partner stopped by picnic tables, a bowling alley and the rooftop hot tub on the base, which borders a working-class neighborhood near downtown. An adult entertainment shop sits on a crime-ridden street near the base; sailors are barred from the thoroughfare.

The most common infraction Tate said he had handled so far were male sailors violating base rules banning earrings. Still, he said he believed his impromptu appearances were helping to keep people in line.

“They know we’re watching them,” he said.

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