The plan to overhaul the military personnel system that Defense Secretary Ash Carter announced Thursday would end the "one-size-fits-all" promotion system for military officers and clear the way for far more diverse options in military career tracks.

For the first time, Carter said he will ask Congress to change key pieces of the "up-or-out" rules for officer promotions and fundamentally place more emphasis on merit rather than seniority. The reforms would clear the way for some troops to pursue nontraditional career paths and for high-performers to climb the ranks more rapidly.

In effect, the Pentagon is asking for Congress to surrender some control over the officer promotion system that lawmakers essentially seized more than 30 years ago with the federal law known as the Defense Officer Personnel Management Act, or DOPMA.

The impact of the reforms would vary greatly among the service branches, various career fields and individual troops. It remains unclear how widespread the changes might be implemented.

Carter rolled out the reforms after months of controversy inside the Pentagon as many senior leaders were skeptical of changing the promotion system that propelled them into the senior ranks.

Carter tacitly acknowledged that and emphasized that he was not seeking a wholesale repeal of the traditional up-or-out system.

"'Up-or-out' isn't broken — in fact, it's an essential and highly successful system — but it's also not perfect," Carter said told dozens of military leaders in the Pentagon's courtyard Thursday. "Most of the time, and for most of our people, it works well. The problem, however, is that DoD can't take a one-size-fits-all approach. And 'most of the time' isn't good enough for the Force of the Future."

The secretary also suggested that, in advocating for key exemptions to the law, he was following through on promises for sweeping reform that he made shortly after taking over the Pentagon's top office last year. "Together, these stand to be the most consequential changes to our officer promotion system in over 30 years, if not more," Carter said.

It's unclear whether Carter's recommendations will become law. The proposal comes as the Senate votes on its draft of the annual defense authorization bill, and as lawmakers from both chambers prepare to start negotiations over a final version to send to the White House for a signature. It is possible that lawmakers could consider the reforms separately, but Capitol Hill grows notoriously unproductive during election years and pushing it through will be a challenge.

Defense officials say some elements of the proposals are in the Senate version of the bill and Carter is confident the measures will draw support on Capitol Hill eventually.

Carter is seeking four specific changes to DOPMA. Two of them would affect lineal numbers and allow troops to voluntarily delay going before a promotion board. Collectively those two changes would incentivize the "career intermission programs" that the services have offered in recent years but are rarely used.

The proposals also seek authority to commission midcareer civilians into paygrades as high as O-6. And Carter is also seeking a broad authority to suspend DOMPA rules for high-demand career fields like cyber warfare.

All of the changes would give the individual services greater authority but not necessarily impose any new rules that the services do not want.

Lineal numbers

A key piece of Carter's reform would give the individual military services authority to adjust the timeline for promotions to make sure top performers move up the ranks more quickly.

Specifically, the top brass could alter an individual service member's lineal number, which determines the order in which officers who are selected by a promotion board are actually promoted for purposes of higher pay and public display of rank

Today lineal numbers are determined by seniority and time in grade." Carter's proposal aims to shift toward a greater emphasis on merit and performance.

The proposal would not change the current "zone" system that defines the pool of officers eligible for promotion.

Changing lineal numbers could result in official promotion up to a year earlier for some top performers.

"It'll help us recognize and incentivize the very best performers — not to mention make promotion even more merit-based than it already is," Carter said Thursday.

Promotion board deferment

A second proposal would allow individual service members to temporarily defer or postpone consideration by a promotion board if they choose.

Some troops may want to do that because the fundamental up-or-out rules will remain in effect, and service members who are considered by a promotion board and passed over twice typically have to separate, ending their military career.

Giving troops the option of deferring a promotion board aims to encourage pursuit of nontraditional career paths. Under the current system, some troops are reluctant deviate from the traditional assignments valued by promotion boards for fear they will be penalized.

Carter pointed to the example of a top young Army officer who recently spent two years as a Rhodes scholar in England and was passed over for promotion repeatedly because he did not have enough time to fill his résumé with traditional Army assignments.

"We can't have a system that inadvertently almost kicks out a Rhodes scholar just because the calendar tells us to," Carter said.

"We need people who've had those kinds of diverse experiences; they help keep us innovative and open to new ideas that can make us better. A Ph.D., a master's, or another experience or form of advanced training doesn't make for a diverted warrior — it makes for a smarter warrior," Carter said.

Lateral entry

A key piece of personnel reform for Carter is changing rules to allow for high-skilled civilians to enter the military at the upper rungs of the officer corps. He is urging Congress to grant authority for the "lateral entry" of civilians up to the rank of O-6, a colonel or Navy captain.

The aim is to create a path into the military for civilian professionals to enter uniformed service without having to start out at the bottom of the rank structure.

Such approvals for lateral entry would only be granted for specific career fields. Carter said it would unlikely be used among the most traditional military careers.

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

"But allowing the military services to commission a wider segment of specialized outside talent … will make us more effective," he said.

For the future

The fourth request that Carter is sending to Capitol Hill is potentially the most far-reaching. Carter is seeking authority for the Pentagon to waive all DOPMA-related rules for entire career fields if needed.

"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," Carter said.

If Congress grants that authority, it would allow future defense secretaries to identify key career fields and grant the service complete control over how and when its officers are promoted.

Questions remain

There are several key steps needed before service members can begin to plan their careers based on these changes.

First, Congress needs to change federal laws. Two elements of the DOMPA changes have been inserted into some drafts of this year's defense bill, specifically the authority to adjust lineal numbers and the authority to grant lateral entry up to the O-6 paygrade.

The two other pieces of DOPMA reform — allowing officers to opt out of consideration for promotion and suspending DOMPA rules for entire career fields — have not.

If Congress approves the new authorities, it remains unclear how much the services will use them. The Navy, for example, has expressed strong interest in these changes. For the Army, Air Force and Marine Corps, the interest level may be lower.

"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.

Absent from Carter's announcement in the Pentagon's courtyard Thursday was a key architect of the personnel reform effort, former Pentagon personnel chief Brad Carson.

Carson led the effort to hammer out the details of Carter's reform proposals, but he resigned in April after wrapping up a slate of recommendations. Carson applauded Carter's final announcement Thursday.

"It is an exciting day," Carson told  Military Times on Thursday after the secretary's speech.

"Today's announcement is historic. These reforms truly mark the most significant personnel reforms in decades, if not since the Department of Defense was established. Secretary Carter deserves great credit for announcing these."