Here is the twitter video of Corporal James Hung reading a recall letter.

https://twitter.com/DonnaPrissyrn1/status/1786913026718711894

There is an active PDF on the Army website that was recently published

"UTILIZATION OF THE ARMY RETIREE RECALL PROGRAM"

Here is the Army website:

https://armypubs.army.mil/ProductMaps/PubForm/Details.aspx?PUB_ID=1028611

Here is the PDF:

https://armypubs.army.mil/epubs/DR_pubs/DR_a/ARN40510-ALARACT_0172024-000-WEB-1.pdf

Note that the PDF mentions 2 Executive Orders,

EXECUTIVE ORDER 13223, was written by Bush in 2001 in response to 9/11. This EO was responding to acts of terrorism.

https://www.presidency.ucsb.edu/documents/executive-order-13223-ordering-the-ready-reserve-the-armed-forces-active-duty-and

EXECUTIVE ORDER 13814, was written by Trump in 2018 and it amended Bush's EO 13223.

"Executive Order 13223 is amended by adding at the end: "The authorities available for use during a national emergency"

https://www.presidency.ucsb.edu/documents/executive-order-13814-amending-executive-order-13223

Edit: I deleted and reposted, I had stupid spelling errors in the first title.