A forward operating site (FOS) or forward operating location (FOL) is a U.S. military term for facilities, defined as "a scalable, 'warm' facility that can support sustained operations, but with only a small permanent presence of support or contractor personnel as opposed to a FOB or MOB.
A FOS will host occasional rotational forces and many contain pre-positioned equipment.
"[1] These sites were established as the Pentagon began to address regional threats primarily in Africa and Latin America following its 2004 global posture review.
[2] An FOS is differentiated from a cooperative security location (CSL) with no permanent force or contractor personnel, or a forward operating base (FOB) and main operating base (MOB), with a large force and a well-defended site.
They include, but are not limited to the following locations: