It started as a joke.
Early last year, President Trump riffed on an idea he called "Space Force" before a crowd of Marines in San Diego.
It drew laughs, but the moment was a breakthrough for a plan that had languished for nearly 20 years.
"I said maybe we need a new force, we'll call it the Space Force," Trump said at Marine Corps Air Station Miramar in March 2018. "And I was not really serious. Then I said, 'What a great idea, maybe we'll have to do that.'"