Defense officials pointed to concerns over the safety of troops coming back from West Africa.
All soldiers returning from the Ebola mission in West Africa will undergo a 21-day quarantine.
Defense Secretary Chuck Hagel ordered military leaders to develop a plan within 15 days on how to carry out the "controlled monitoring regimen" for the approximately 4,000 troops that could be involved in the military's Ebola operations, said Rear Adm. John Kirby, the Pentagon press secretary, in a statement Wednesday.
Hagel "believes these initial steps are prudent given the large number of military personnel transiting from their home base and West Africa and the unique logistical demands and impact this deployment has on the force," Kirby said. "The secretary's highest priority is the safety and security of our men and women in uniform and their families."
The decision to quarantine all troops will be reviewed after 45 days to determine "whether or not such controlled monitoring should continue."
The military-wide quarantine decision comes two days after Army leadership announced that all of its troops involved in the Ebola mission would undergo a quarantine.
Kirby, on Tuesday, defended the military's decision to even consider a quarantine for troops who won't be coming into contact with Ebola patients. Such a move goes beyond the recommended Center for Disease Control and Prevention guidelines released Monday. CDC Director Tom Frieden said that "high-risk individuals," including those who cared for someone suffering from Ebola without wearing protective gear, should voluntarily isolate themselves within their homes.
"Nothing has changed about the fact that we hold their safety and their security to be our prime responsibility," Kirby told reporters. "The secretary is very committed to that."