President Trump, right, and Defense Secretary Jim Mattis. (Mandel Ngan/AFP/Getty Images)

PRESIDENT TRUMP seems to be trying to make his Space Force seem like a dumb idea. He appears to have sprung the idea without warning on everyone who would have to make it happen. His 2020 campaign is hawking merchandise with slogans such as “Mars Awaits.” Even the name sounds silly.

In fact, the idea is not silly. But those who counsel caution about a big bureaucratic reshuffling at the Pentagon have the better side of the argument.

The Space Force would not land troops on Mars. It would take responsibility for the nation’s fleet of unmanned orbiting vehicles that power GPS, weather prediction, reconnaissance and other essential needs.

Those favoring a Space Force argue that the Air Force, which controls 90 percent of the unclassified national security space budget, is dominated by fighter pilots who have neglected space defense, even as international rivals develop their orbital capabilities. There is a distressing lack of redundancy on crucial systems, the downing of which could blind the military and crash the world economy. A new military branch might better advocate the interests of space assets. Moreover, all the services use space-based platforms, so it may not make sense for the nation’s space organization to cater to Air Force brass.

Yet, the Pentagon has hardly ignored space. Its 159 satellites represent the largest fleet of any single organization in the world. The Air Force’s Space Command boasts a budget of $8.5 billion and 36,000 employees. Far more goes to the classified space operations that the intelligence community controls. More may be needed, but the Brookings Institution’s Michael O’Hanlon pointed out that splitting the Air Force might not be the way to increase its or the new Space Force’s pull in Congress. It would be simpler to promote officers who work on space issues to the highest levels of the Pentagon or centralize budgeting for military space operations. Moreover, it is far from clear that creating a new independent Pentagon fiefdom would promote any more integration with the Army or Navy. After its creation, the Air Force struggled for decades to cooperate with the other branches.

For now, it is unclear whether a big, new military reorganization would add anything useful to what the administration is already doing — setting up a joint space command, putting more emphasis on developing new space military technologies and pushing harder for the cultivation and promotion of space-oriented officers and specialists. The administration should step up these efforts, not inaugurate a massive bureaucratic overhaul that could for years prove a diversion and distraction.

It would be costly to stand up a brand-new branch of the military, with its own academy, uniforms and so forth. The burden is on advocates for a new service to show that the money would be well spent. They have yet to do so.