The air force of Tito's Yugoslavia has had many different peculiarities - from a unique Cold War position of having operated a mix of US, Soviet, and indigenous aircraft and equipment, to the changeable strategies in case of war.
One such feature was an entire underground air base constructed inside a hill near the town of Bihac, in western Bosnia. The Object was the core, the heart, of this air base: it housed four MiG-21 squadrons for nearly 25 years, until the civil war tore Yugoslavia apart.
The Object was built as the outcome of Yugoslav military efforts to build up its independent defence capabilities, especially the air force which was regarded as the strategic tool in keeping Tito's Yugoslavia's independence from both Cold War blocks.