US Air Force General John "Jay" Raymond was sworn in by US Vice President Mike Pence on Tuesday in Washington as Chief of Space Operations.
US Space Force is the seventh branch of the US military.
"It is President [Donald] Trump's belief that the United States must remain as dominant in space as we are on land and sea and the air. And your charge is to see to that mission with the United States Space Force," Vice President Pence said at the ceremony.
Gen Raymond, a four-star general, already wears a pair of other hats – commander of the Air Force Space Command and the US Space Command.
He said he was ready to get on with the job.
"Mr Vice President, we have our marching orders and we are moving out. We do not want a conflict to begin or extend into space. We want to deter that conflict from happening. The best way I know how to do that is to do so from a position of strength,” he said.
US National Public Radio observed that right now there are no Space Force troops for Gen Raymond to command.
That will eventually comprise around 16,000 personnel, most from the USAF and mostly drawn from the US Space Command, to be the Space Force's operational component.
It may not yet have personnel but it does have funds.
Congress provided US$40 million in the 2020 defence budget to stand up Space Force. It will operate under the umbrella of the USAF in much the same manner as the US Marine Corps operates under the US Navy.
Gen Raymond, who will be a member of the Joint Chiefs of Staff, has long been an advocate for creating a military branch focused on space.
He told reporters in the US last year that the scope, scale and complexity of the threat to US space capabilities was real and concerning.
"We no longer have the luxury of operating in a peaceful, benign domain, and we no longer have the luxury of treating space superiority as a given," he said.
Gen Raymond sees the new military thrust into space as a collaborative effort with allies.
"Historically, we haven't needed to have allies in space,” he said.
“Space was a benign domain, it wasn't as critical. It is very important today that we have — and we are working very closely with our partners, specifically our Five Eyes partners.”
The Five Eyes comprises the US, UK, Australia, New Zealand and Canada. Ally partners include France, Germany and Japan.
This will also involve commercial collaboration and Gen Raymond has already talked to space entrepreneurs Elon Musk, Jeff Bezos and Richard Branson.
"Early in my career as a young captain, I was the commercial space officer for Air Force Space Command. So, I have been steeped in interfacing with the commercial business for many, many years,” he said.
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