Satellites make much of modern warfare possible, through GPS systems, wireless communications and sophisticated weather forecasting. This makes them tempting military targets. The U.S. Air Force has been responsible for defending American satellites and spacecraft. President Donald Trump said in 2018 that the perils required a new military branch, an idea that came to be known as the Space Force. The idea was popular with crowds at the president’s rallies, but not with Pentagon officials or many in Congress. After months of debate, Trump signed an order creating a more modest Space Force that would sit within the Air Force, similar to how the Marine Corps sits within the Navy.

1. What would a Space Force do?

In a report to Congress released in 2018, the Department of Defense laid out a plan to build a new force to defend U.S. interests in space with aggressive offensive capabilities. This would include systems that could “degrade, deny, disrupt, destroy, and manipulate adversary capabilities.” The force would hold joint space training and military exercises with U.S. allies.

2. Is there a true military threat in space?

Yes, but not in the Hollywood sense of alien invaders attacking lower Manhattan. The main threat is the ability to disable or destroy an adversary’s satellites from the ground. In 2007, China first used a ballistic missile to destroy its own old weather satellite orbiting 535 miles (861 km) above Earth; Russia has been testing a missile that could be used to strike and destroy a satellite or ballistic missile. It’s likely that other nations won’t be far behind. If you destroy a spy satellite, the flow of real-time intelligence from a particular spot in China or Iran could stop. A communications satellite that’s jammed from the ground could mean ground troops suddenly find themselves operating blindly. And because existing international treaties governing space are unclear, even civilian satellites could be targeted by nations looking to contain or punish their enemies.

3. How would the new force defend space?

The U.S. military was already working on systems to protect satellites from threats like jamming and destruction by “kinetic” objects, such as missiles or other satellites. And there’s a top-secret Air Force aircraft, the X-37B, which has orbited Earth for expanded periods; its missions are unknown. In a speech on Aug. 9, Vice President Mike Pence said American should have “dominance in space.” A Space Force could mean bigger research and development budgets. Some in Congress have called for weapons that could destroy ballistic missiles from space. On a more workaday level, the Space Force would likely take over the job, now performed elsewhere in the Air Force, of tracking the world’s active satellites to make sure they don’t collide with one another or with space debris and to notify owners to reposition their satellites if there’s a possibility of impact.

4. Can the U.S. put weapons in space?

Yes. The 1967 United Nations Outer Space Treaty, which bans weapons of mass destruction in space, prohibited orbiting nuclear weapons. But it didn’t prohibit other weapons. In an interview with Bloomberg in October, the head of the Air Force Space Command, General John W. “Jay” Raymond, said that “our goal is not to have conflict in space.” But, he added, space is “a war-fighting domain and we need to treat it as such.”

5. How would the force get started?

Congress would need to authorize it first, something it declined to do last year. Trump now has directed the Defense Department to send a legislative proposal to Capitol Hill that would establish Space Force as a sixth military service branch within the Department of the Air Force, something that’s seen as a politically easier step. The proposal also calls for a Space Force chief of staff who would be a member of the Joint Chiefs and confirmed by the Senate.

6. How much would it cost?

Congress will decide that as part of the budget process. When he made his pitch for an independent Space Force, Trump called on Congress to allocate $8 billion over the next five years for space security systems. But the administration may request just $100 million of new funding in its fiscal 2020 budget next month, a senior administration official said. The Air Force now gets more than $11 billion for its space programs — the bulk of the Defense Department’s unclassified national security space programs, according to the Pentagon’s fiscal 2019 budget request.

7. Was the Space Force Trump’s idea?

No, though he was the first president to publicly call for a separate military branch for space. The debate over space militarization dates to at least the Cold War, when the U.S. and Soviet Union first realized that controlling space could give them an edge in a conflict. In 1982, the investigative arm of Congress urged the creation of an “aerospace force” or “space force” to develop “laser battle stations in space” that could defend against a Soviet ballistic missile attack. The following year, President Ronald Reagan called for such a system, the Strategic Defense Initiative, which critics nicknamed “Star Wars.” (It never advanced beyond the research phase; its successor, the Missile Defense Agency, uses Earth-based systems like Thaad to destroy missiles at high altitudes.) In early 2001, a commission led by former Secretary of Defense Donald Rumsfeld concluded that the U.S. wasn’t prepared to defend its enormous dependence on satellites. In 2017, House of Representatives members led by Representative Mike Rogers, an Alabama Republican, began pushing for a new “ space corps.”

8. What was the argument for taking it from the Air Force?

The argument for a new military arm rested on the notion that Air Force brass focus their budgets — and priorities — on conventional air superiority, and manage space as only an ancillary theater of conflict. But the Air Force considers space defense as one of its core missions and has had a Space Command since 1982. Air Force officials — and Defense Secretary Jim Mattis — argued that setting up a separate space branch would add bureaucratic layers and slow down existing research and programs. An independent Space Force might have led Congress to pare the Air Force budget, or other parts of Pentagon or overall spending, to help pay for the new branch.

9. Do other countries have military space forces?

Yes. Russia created its Aerospace Forces in 2015. China’s space program was always part of its military; in 2015 the People’s Liberation Army added a Strategic Support Force in part to coordinate all the military’s space-related capabilities.