The new measure is most likely caused after a heatmap, generated by the activity of users of the fitness app Strava, revealed the locations of U.S. military bases in foreign countries. Their use in overseas locations "potentially create unintended security consequences and increased risk to the joint force and mission", Manning said.
The Pentagon is banning the use of Global Positioning System on mobile devices in war zones and other sensitive locations, saying that fitness trackers and smartphone apps pose a "significant risk" to US military personnel.
The announcement comes after news stories surfaced earlier this year that fitness apps such as Polar Flow and Strava have been inadvertently giving away locations and habits of USA service members on installations around the world.
"The biggest concerns with the data is firstly it allows an unprecedented look at the geographic build of a lot of these bases", Ruser told ABC News in January. "But more than that, one of the most important and disturbing elements of the map is that it's possible to establish an understanding of how the base works". Within the U.S., the colorful web of lines was mostly just an interesting way of visualizing runners' data, but in Middle Eastern countries such as Afghanistan, the map showed much more.More news: Saudi airline stops flights to Canada amid escalating diplomatic row
The Aug. 3 memo, first reported by The Associated Press, does not completely ban the fitness trackers or other electronic devices, but orders that they must be turned off in certain operational areas "effective immediately".
At the time, the Pentagon insisted that the classified or sensitive locations of USA service members had not been compromised by the data.
The Pentagon in May tightened some of its policies on the use of mobile phones in the building after a months-long review on the issue. Shanahan's memo also gave the military's combatant commanders guidance on how to seek authorization for the use of geolocation features should they deem it necessary.
"It goes back to making sure that we're not giving the enemy an unfair advantage and we're not showcasing the exact locations of our troops worldwide", Manning said.More news: Superyacht linked to 1MDB probe arrives at Malaysian port
While the devices themselves will not be banned, service members will be responsible for ensuring their geolocation features are disabled.
"It's a necessary evolution", he added.
Army Col. Rob Manning, a Pentagon spokesman, said it's a move to ensure the enemy can't easily target US forces.More news: NASA announces astronauts for SpaceX and Boeing launches from the US