Trump opens the door to calling up former active service members for coronavirus fight

"This will allow to us mobilize medical disaster and emergency response personnel to help wage our battle against the virus by activating thousands of experienced service members including retirees," Trump told reporters Friday.

The order grants the Defense secretary the authority to order up members, but as of now there is no indication of that happening. Such a call is usually used when the military is in need of specific skill sets.

"Decisions about which individuals may be activated are still being reviewed. Generally, these members will be persons in Headquarters units and persons with high demand medical capabilities whose call-up would not adversely affect their civilian communities," Jonathan Hoffman, the Pentagon's chief spokesman, said in a statement late Friday.

"This is a dynamic situation, we do not currently have a projected number of expected activations, but the Department is now fully authorized to make activations as needed," Hoffman said.

In most cases, after concluding their military obligations, service members will enter into what is known as the Individual Ready Reserve.

That ready reserve status requires no active participation, leading the vast majority of service members to consider being in that status the same as being out of the military. Most service members are in that designation for a period of years.

There have been a handful of cases in the past where members of this reserve have been called up for active duty -- such as during the height of both Iraq wars.

Trump said Friday that "we have a lot of people, retirees. Great, great military people. They're coming back in, who have offered to support the nation in this extraordinary time of need."

"And they come back in. They don't say, 'How much?' They don't say, 'What are we getting paid?' They just want to come back in. It's really an incredible thing to see. It's beautiful," he added.