"The purpose is to make sure that we're not bringing the virus back home, infecting others, that we're not spreading it around the military," Esper said of the move, first reported by Reuters on Wednesday.
In a statement, the Pentagon said the stop-movement order impacts "exercises, deployments, redeployments and other global force management activities," affecting approximately 90,000 service members slated to deploy or redeploy over the next 60 days. Exceptions include travel for medical treatment and scheduled deployments of U.S. Navy vessels.
DOD also on Wednesday raised its Health Protection Condition (HPCON) level globally to "Charlie" -- the second highest level which indicates sustained community transmission.
Only essential personnel will be allowed onto military bases worldwide and the installations will limit entry points. Personnel on the bases will also be required to practice social distancing, officials said.
These moves are just some of the ways the Pentagon has steadily increased restrictions on its personnel and implemented measures aimed at mitigating the spread of the deadly virus over the last several weeks.
As of Wednesday morning, the Pentagon confirmed that 227 service members had tested positive for COVID-19 -- up from 174 confirmed cases the previous day.
Those individuals now include three Navy sailors aboard a U.S. aircraft carrier, an Army recruit training at Fort Jackson in South Carolina, a Marine stationed at the Pentagon and more than two dozen members of the National Guard.
And while the department has suspended several overseas military exercises with partner nations and training efforts in Iraq and Afghanistan, it has allowed training stateside to continue largely unchanged.
Asked in a town hall event on Tuesday why units were still congregating in formations, Esper said the department has to maintain readiness, including physical fitness.
"You can't get social distancing in a submarine or even in a tank, right? I've been in both," he said. "But you take prudent measures as best you can, given the situation you're in, given your mission and whatnot."
He continued, "That's what we call upon commanders and senior (non-commissioned officers) at all levels to do: assess their situation, and if you can avoid putting people in -- a large number of people -- in small rooms, you should do it. Hold your meeting outside, or maybe meet in smaller groups. Get that social distancing as best you can."
Still, during the same town hall, Chairman of the Joint Chiefs of Staff Gen. Mark Milley conceded the changes made to prevent the spread of the virus will have an impact on military readiness.
"There will be an impact to readiness, but I think it will be on the lower end as opposed to significant," he said.
At the same time the department is working to protect the force, it's also providing personnel and resources to state governments whose health care systems are expected to be overrun with patients suffering from the virus.
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On Friday, the Navy hospital ship USNS Mercy is set to arrive in Los Angeles. And three Army field hospitals are being deployed this week to New York and Washington.
There are also more than 10,700 National Guard personnel currently responding across 50 states, three territories and the District of Columbia.