Defense Secretary Ash Carter announced that he would end the “one-size-fits-all” promotion system for military officers, Military Times reported. This could open up more opportunities for diverse military career options.

Carter’s “Force of the Future” reform was announced June 9.

“It aims to help the military bring in more top talent, especially for high-tech career fields focused on cyber warfare and space,” according to a Military Times article. “Advocates say it will help the military fill important manpower shortfalls with highly skilled professionals and, more broadly, create greater ‘permeability’ between the active-duty military and the civilian sector.”

Many of the changes Carter intends to make will need Congress to change the Defense Officer Personnel Management Act, a law concerning most aspects of military promotion, according to Federal News Radio. Carter said the Defense Department will focus on four specific changes, “including a relaxation of the ‘up or out’ promotion process, which he said is fundamentally sound, but too rigid,” Federal News Radio reported.

Carter is requesting that the Pentagon waive all DOPMA-related rules for career fields, if necessary.

According to Carter, this will “ enable them to respond to an uncertain future, in ways that can be tailored to their unique capability requirements and particular personnel needs, without casting off a system that still largely meets our needs for most officers across the force”

One significant change is the opportunity for “lateral entry” into the upper ranks of the military. Promotions will be based on performance rather than tenure in a position. Military services would have the ability to do this, but it would not be required.

Lateral entry will also mean civilian professionals will not have to start at the bottom of the ranks, according to Military Times.

“Now, I have to say we can’t do this for every career field — far from it,” Carter said. “It will probably never apply to line officers, as they’ll always need to begin their military careers as second lieutenants and ensigns.”

These changes are not without controversy and opposition.

“For many in the rank-and-file military, it seems absurd, a bewildering cultural change that threatens to upend many assumptions about military life and traditional career paths,” wrote Andrew Tilghman for Military Times.

Military Times also reported that the U.S. Navy is the most enthusiastic about Carter’s proposal. The Army and Air Force have said they will consider lateral entries if the change is approved by Congress. The Marine Corps seems to be the most wary of the changes. One Marine personnel officer said he supports the proposal because it does not require services to make changes.

“We are prepared to observe the ‘experimentation’ efforts of other services and adopt the best practices where applicable and advantageous,” said Col. Gaines Ward, head of the service’s promotions and policy branch, as reported by Military Times.

Each military service would be able to work out which changes to implement for themselves.

“It’s up to the services. We’re not trying to bind them in, were offering to give them flexibility,” said a senior defense official.