The president described in March how he had originally coined the term as a joke, while discussing U.S. government spending and private investment in space. Trump then directed the Pentagon in June to immediately begin the creation of the new branch.

Trump first floated the Space Force idea as a part of his national security strategy March 13. On Thursday, he expressed his enthusiasm for the plan in a tweet shortly after Pence made the announcement, saying: "Space Force all the way!"

Vice President Mike Pence announced the Pentagon's detailed plan for President Donald Trump 's vision of a Space Force on Thursday, which would establish the first military branch in over 70 years.

Pence on Thursday stressed that the new branch would be built, in part, from pre-existing elements.

"The Space Force will not be built from scratch," Pence said during a speech before members of the Pentagon. "This is a critical step toward's establishing the Space Force as the sixth branch of our armed forces."

Here are the four components to the Department of Defense establishing a Space Force:

First, DoD will establish a Space Development Agency to develop and field space capabilities at speed and scale. The Air Force has already begun to transform its Space and Missile Center (SMC). The Department will accelerate and extend this transformation to all services by creating a joint Space Development Agency. Second, the Department will develop the Space Operations Force to support the Combatant Commands. These joint space warfighters will provide space expertise to combatant commanders and the Space Development Agency, and surge expertise in time of crisis to ensure that space capabilities are leveraged effectively in conflict. Third, the Department will create the governance, services, and support functions of the Space Force. Many of these will require changes to U.S. law. The Department will build a legislative proposal for Congressional consideration as a part of the Fiscal Year 2020 budget cycle. Fourth, the Department will create a U.S. Space Command, led by a four star general or flag officer, to lead the use of space assets in warfighting and accelerate integration of space capabilities into other warfighting forces. U.S. Space Command will be responsible for directing the employment of the Space Force.

Defense Secretary James Mattis on Tuesday threw his support behind the idea of creating a space-focused military command but stopped short of promising the new "Space Force" branch of service that Trump has touted. Currently the U.S. Air Force manages the domain through the U.S. Space Command.

"We need to address space as a developing war-fighting domain and a combatant command is certainly one thing that we can establish," Mattis told reporters at the Pentagon, adding: "This is a process we're in."

The Pentagon's top brass is hesitant to form a new military branch, former Air Force secretary Deborah Lee James told CNBC on July 30.

"None of them are in favor of a space force but they are stuck," James said. "The president has said it and it will be interesting to see how they now deal with it."

Read the full Pentagon report to Congress here: