Donald Trump said Monday that he had directed the Pentagon to establish a Space Force, describing it as a sixth branch of the U.S. military. It would be the first time the Pentagon has stood up a new service since the Air Force received its independence after World War II.

Creating a standalone service for space isn’t something the president can do on his own; he needs congressional authorization. But Monday’s announcement (here's video, via Reuters), which follow broad endorsements of the concept by the Joint Chiefs’ office and various military branches, means that Senate holdouts who were taking their cues from the Air Force are likely to bow out of the fight.

That could clear the way for a Space Force to be in the 2019 defense authorization act, says Todd Harrison, who directs the Center for Strategic and International Studies’ Aerospace Security Project.

It wasn’t immediately clear just what parts of the Pentagon’s sprawling space endeavors would be swept into this new outfit. Most of the Navy’s space-and-satellite work falls under the Space and Naval Warfare Systems Command, based in San Diego, while the Army has its Space and Missile Defense Command in Huntsville, Ala. But the bulk of the military’s space efforts are handled by the Air Force — specifically Air Force Space Command at Peterson Air Force Base, Colo. — and it has been the air service that has fought hardest against the idea.

It wasn’t even clear whether the new service branch would have its own secretary, putting it on par with the Army, Navy, and Air Force — or would occupy a lower tier, like the Marine Corps. Trump seemed to suggest the former. "We are going to have the Air Force and we are going to have the Space Force, separate but equal," he said, carefully enunciating the oddly infelicitous phrase.

The announcement caught some in the Pentagon by surprise. "We understand the President's guidance. Our Policy Board will begin working on this issue, which has implications for intelligence operations for the Air Force, Army, Marines and Navy. Working with Congress, this will be a deliberate process with a great deal of input from multiple stakeholders," Pentagon spokesperson Dana W. White said in a statement.

The military was in the process of evaluating the entire space force concept in terms of feasibility and structure. Deputy Defense Secretary Patrick Shanahan’s office was conducting what Harrison described as a broad study due in August.

A potentially more interesting study, due in September, was to be completed by the Center for Naval Analysis. “Their job was to create a roadmap for how to create an independent service for space. They’re supposed to be coming up with the plan for how to do this. They would give it to Congress to consider for next year’s NDAA,” said Harrison.

To some, Monday's announcement smacked of impulsiveness. “This is another example of: ready, fire, aim,” said David Deptula, a retired Air Force lieutenant general who leads the Mitchell Institute for Aerospace Power Studies.

One former Air Force chief of staff urged a more gradual approach to establishing a Space Force. “I think we need at this point in our history to think about setting up a force that can answer the question: ‘What are you going to do when you have to fight in space?'" said Merrill “Tony” McPeak, who led the service from 1990 to 1994. "I think we’re poorly equipped to do that until we have a service that grows people from the beginning to be Coneheads and Star Trek warriors, not fighter pilots or bomber pilots and transport pilots or anybody who knows how to operate in an air-breathing environment.”

McPeak said it would be best to keep the Space Force under the Air Force umbrella, “although eventually I think it would migrate totally into its own department, and should.”

What would a Space Force actually do? Harrison suggested that the most useful thing would be to create a “cadre of space professionals. [It would] groom them and grow them to think space, space power, strategy, doctrine, and to develop more innovative operational concepts.”

He added, “It doesn’t mean that space will become more weaponized or militarized; that’s happening anyway, regardless of what the United States does. The weaponization of space is being led by other countries."

In the decades before the Air Force’s creation, a cadre of aviators developed airpower doctrine and strategy at the Army Air Corps Tactical School. That has not been the case this time around, said Doug Birkey, executive director for the Mitchell Institute for Aerospace Power Studies. The military has treated space airmen as technical experts providing a utility, Birkey said, largely because talking about offensive wars in space has been taboo.

Policy makers “need to think about how to use space as a national military asset, not just Verizon” — a telecom utility, Birkey said.

He said that if lawmakers create a Space Force, it’s essential that space specialists in the Army, Navy, and Marine Corps also get put into the new branch.

Space has at times been seen as the Air Force’s red-headed stepchild, playing second fiddle to go-fast jets. After Strategic Air Command shut down, its ICBMs were shuffled to Space Command, until the creation of Global Strike Command some 17 years later. This summer, the cyber warfighting arm of the Air Force will move from Space Command to Air Combat Command.

Air Force leaders — who have been opposed to creating a new space service — have made a number of moves that they say show they take the space mission seriously.

The concept of a standalone service for space received some top-level support under Donald Rumsfeld and in the 2000 National Defense Authorization Act. More recently, Rep. Mike Rogers, R-Ala., and Jim Cooper, D-Tenn. — the chairman and ranking member of House Armed Services Committee’s strategic forces panel — pushed the House to include a Space Force amendment in its version of the 2018 NDAA. The provision was ultimately axed in negotiations with the Senate.

But today’s announcement goes beyond what Rogers and Cooper sought, which was a Space Corps whose commander would answer to the Air Force Secretary, just as the Marine Corps answers to the Navy Secretary. A Space Force, however, would be independent entirely from the Air Force, potentially with its own Secretary.

The chief study that Space Corps (or Force) proponents cite for the necessity of such a thing is a May 2017 Government Accountability Office report that concluded that the way the Air Force was buying space capabilities was leading to cost overruns and schedule delays.

The military has been expanding its outreach to commercial satellite providers to offer secure communications capabilities and, potentially, to host intelligence, surveillance and reconnaissance payloads, one of many signs showing that private sector is moving more aggressively than government entities in terms of putting new assets into orbit.

The U.S. military’s ambitions for space, and its recognition of space as a domain critical to communications and economic security, is on a crash course with “an acquisition process that doesn’t allow you to get there until the late 2020s,” retired Gen. Robert Kehler, a former commander of U.S. Strategic Command, told lawmakers in March.

Among those ambitions: satellite-based weapons that destroy enemy ballistic missiles with particle beams, a Cold War idea that is making a comeback under Michael Griffin, the first defense undersecretary for research and engineering.