I do remember reading on the SDSR 2015 that up to 10.000 troops could be deployed on the streets to support Police forces in case of an attack.
@Blue Marlin
France currently deploys 7.000 to 10.000 soldiers (mainly from the ground forces,but also from the navy and air force)to patrol the streets and public places,sometimes in cooperation with the Gendarmerie and the Police Nationale. Mobile patrols are organized around important and strategic places. In most of the cases,they patrol on 3,one leading,two behind. But sometimes could be higher.
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Personnels from the navy.
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There are many advantages like disadvantages of deploying the army on the streets. Of course,this is on a French point of view.
They can be seen as a deterrent,able to intervene quickly on an incident,and to make the public feel safer. On the other hand,this diverts them from their main mission as soldiers aren't here to do Policing missions.
They are also a visible and strong magnet of people with bad intentions and terrorists willing to kill anyone representing any authority. There were many incidents against them. Such as what happened few days ago in Orly airport and in the Louvres museum.
Of course,they do their missions with pride while the politicians and the public strongly support this deployment,even if some are questonning it.