Definition: Property operated and mostly exclusively used by foreign military forces (and only supported by national forces).
This definition includes bases in overseas territory, even if it formally belongs to the same nation (concerning USA, UK and FR and CN).
Note: Embassies and consulates are generally not included, although U.S. facilities all over the world play an important role as spy listening stations and other activities with military importance.
Unnamed Airfield (Syria)
The North-east region of Syria is officially under control of the Syrian SDF, who are cooperating with the illegal deployed US forces. Without any doubt all military locations with airfields must be under control and funded by US forces.
Five Eyes Station Lerkil (Sweden)
This spy listening station is not marked with a military layer in OpenStreetMap, but clearly belonging to NSA activities based on the Five Eyes espionage cooperation.
South Chinese Sea
Several very small islands and atolls in the South Chinese Sea are claimed by China, which has made military facilities on these locations. But there are also claims from other countries, what is no subject for discussion in VisualBases. These locations are overseas bases from China.