WASHINGTON — President Biden signed an executive order on Friday giving decisions on the prosecution of serious military crimes, including sexual assault, to independent military attorneys, taking that power away from victims’ commanders.

The order formally implements legislation passed by Congress in 2022 aimed at strengthening protections for service members, who were often at the mercy of their commanders to decide whether to take their assault claims seriously.

Members of Congress, frustrated with the growing number of sexual assaults in the military, fought with defense leaders for several years over the issue. They argued that commanders at times were willing to ignore charges or incidents in their units to protect those accused of offenses and that using independent lawyers would beef up prosecutions. Military leaders balked, saying it could erode commanders’ authority.

The change was among more than two dozen recommendations made in 2021 by an independent review commission on sexual assault in the military that was set up by Defense Secretary Lloyd Austin. And it was included in the annual defense bill last year. But since it requires a change to the Uniform Code of Military Justice, it needed formal presidential action.

In a call with reporters previewing the order, senior Biden administration officials said it was the most sweeping change to the military legal code since it was created in 1950.

The Pentagon had already been moving forward with the change. A year ago, the Army, Navy, Marine Corps, and Air Force set up the new special trial counsel offices, which will assume authority over prosecution decisions by the end of this year. Beginning Jan. 1, 2025, that prosecution authority will expand to include sexual harassment cases.

The changes come as the military grapples with rising numbers of reported sexual assaults in its ranks.

While the services have made inroads in making it easier and safer for troops to come forward, they have had far less success reducing the number of assaults, which have increased nearly every year since 2006. Overall, there were more than 8,942 reports of sexual assaults involving service members during the 2022 fiscal year, a slight increase over 8,866 the year before.

Defense officials have long argued that an increase in reported assaults is a positive trend because so many people are reluctant to report them, both in the military and in society as a whole. Greater reporting, they say, shows there is more confidence in the reporting system, greater comfort with the support for victims, and a growing number of offenders who are being held accountable.