For John, BLUF: Retired Military personnel are liable to call up even after retirement, but only up to a certain age.  Those in their 70s are exempt. On the other hand, males 17 to 45, even without prior service, are liable to call up, in extremis, under the Dick Act. Nothing to see here; just move along.
More than 9,000 retired Army medical personnel respond to call for assistance with coronavirus pandemic
Here is the sub-headline:
Hundreds of active duty soldiers are also deploying to support field hospitals.
From ABC News, by Ms Elizabeth McLaughlin, 27 March 2020.
Here is the lede plus three:
More than 9,000 retired soldiers have responded to the U.S. Army's call for retired medical personnel to assist with the response to the novel coronavirus pandemic, as hundreds of active duty soldiers deploy to support Army field hospitals in New York and Seattle.Notice in the last paragraph quoted that there is a mobilization process. It isn't instantaneous. The person activated needs to be transported to the new unit and then given a job.
Earlier this week, the Army sent a notification to more than 800,000 retired soldiers to gauge their willingness in returning to service in a volunteer capacity. In a Pentagon briefing on Thursday, Army Chief of Staff Gen. James McConville called the initial response "very, very positive."
Army Surgeon General Scott Dingle told reporters that these volunteers will "fill those holes" in military medical treatment facilities across the nation where some staff are now deployed to field hospitals, leaving vacancies in their traditional assignments.
"What we'll do is even though we get many volunteers, we then will walk through the process of certification, making sure that all certifications and credentials are straight," Dingle said. "Then once we do that, we will plug them into all of our medical treatment facilities as required in support of the mission."
Hat tip to the InstaPundit.
Regards — Cliff