WASHINGTON (AP) — The U.S. military on Thursday opened a new chapter in how it investigates and prosecutes cases of sexual assault and other major crimes, putting independent lawyers in charge of those decisions and sidelining commanders after years of pressure from Congress.

The change, long resisted by Pentagon leaders, was finally forced by frustrated members of Congress who believed that too often commanders would fail to take victims' complaints seriously or would try to protect alleged perpetrators in their units.

The new law was fueled by a persistent increase in sexual assaults and harassment across the military. The Air Force, the Marine Corps and the Navy all saw reported sexual assaults go up last year, but a sharp 9% drop in reports from the Army — the largest military service — drove the overall number down. In 2021, reported assaults spiked by 13%.

Under the law, new special counsels will have the authority to make prosecution decisions on a number of major crimes, including murder, rape and several other sexual assault-related offenses, kidnapping, domestic violence, making or possessing child sexual abuse images, stalking and retaliation.

In a statement, Secretary of Defense Lloyd J. Austin III called it "the most important reform to our military justice system since the creation of the Uniform Code of Military Justice in 1950."

It's unclear, however, what impact the change will have on the broader problem of sexual misconduct in the military, including if it will trigger an increase in prosecutions and, if so, whether that will have any deterrent effect.

Senior officials from the military services who are familiar with the new program said they already have more than 160 certified special trial counsels who will take over the prosecution decisions as of Thursday. Many of those lawyers, however, have already been involved, providing advice and support for months on cases that are underway. The officials spoke to reporters on the condition of anonymity to discuss the new program under rules set by the Defense Department.

As of Thursday, the special trial counsels will have sole authority to make prosecution decisions on new cases involving the major crimes. Any advice on already existing cases is nonbinding, the officials said.

According to the officials, the Army will have 65 certified trial counsels, the Air Force will have 40, the Marine Corps will have 33 and the Navy will have 24, with 23 attorneys who are not yet certified assisting in the cases. About 10 more are expected to be certified in the summer.

The lawyers will be scattered around the U.S. and the world, with larger numbers at bases and locations where there are more service members and more crime.

The officials said they expect each trial counsel to handle as many as 50 investigations and roughly eight to 12 trials a year.

An independent commission that studied sexual assaults in the military suggested in its report that the use of special counsels would have a positive impact. It said the special counsels would make better decisions on what cases should go forward, resulting in higher conviction rates. Increased convictions, the report said, will encourage more accused perpetrators to make plea agreements, which alleviates the need for victims to testify at trials.

"These outcomes will also increase confidence in the public that the military is correcting its course in the prosecution of special victim cases," the report said.

Sean Timmons, managing partner at the Tully Rinckey law firm, which specializes in military cases, said the change doesn't really get at the underlying behavioral problems. As a result, he said, it is unlikely to have any real impact or deterrent effect on misconduct by service members. He said that it could result in more people being fired as a result of board proceedings but that in agreements in which the victims don't testify, the cases may end up being weaker.

"My analogy of that is we're rearranging the chairs on the Titanic," said Timmons, a former Army judge advocate general. "Nothing will really change other than semantics and appearances. That's the unfortunate reality."

The military services have long struggled to come up with programs to prevent sexual assaults and to encourage reporting, including a number of new initiatives in recent years. But they have yet to show any real progress in lowering the number of reported assaults, and anonymous surveys still indicate that many more victims opt not to report.

Defense officials have long argued that an increase in reported assaults is a positive trend, both in the military and in society as a whole. Greater reporting, they say, shows there is more confidence in the reporting system and the support available for victims.

Nate Galbreath, acting director of the Pentagon's sexual assault prevention and response office, said in April the department was using a budget infusion of $479 million this year to hire as many as 2,400 personnel for a new prevention workforce. He said about 350 had already been hired and as the number grew they would be placed in military installations around the world to help commanders address some of the risk factors that lead to sexual assault.