The fictional army base in Grand Theft Auto 5 is in Blaine County, San Andreas, and is on the outskirts of the Lago Zancudo swamp. This military installation is called Fort Zancudo and is the only base located in the game, as of 2014. There are two runways located inside the military base.
Fort Zancudo is bordered by the Zancudo River to the south and Route 1 to the west. The base serves as the main munitions depot and airfield for the U.S. Air Force within the GTA 5 game universe. Phrases shouted by soldiers stationed at the base suggests that the U.S. Marine Corps is present. Badges found on soldiers from the base suggest that U.S. Army personnel are stationed there as well, making Fort Zancudo a multibranch military base. The location is heavily guarded and protected along its perimeter by an antiscale fence. Roads leading to the base are dotted by military checkpoints manned by armed guards. On the base, there are three large hangars as well as a munitions depot. The airspace over the base is restricted and warnings are issued to any player flying a vehicle. Players caught flying over the area are automatically issued a two-star wanted level.