Germany began moving some of its critical factory operations underground in response to increased allied bombing in the later stages of World War II. Most factories were built in former mine sites and were built, and staffed by slave labor. These factories built critical components for super weapons, including V-1 and V-2 rockets, and German jet aircraft. To resist allied bombing, Germans also used underground sites to store fuel.
Germany may build underground factories for the cost of 8 IPC per factory. The factory may be built anywhere a major or minor industrial complex can be built but may not be upgraded.
The factory may only be used to construct one unit per turn but may not be tactically/strategically bombed. An underground factory may not produce or repair ships or produce infantry.
Any player may build an Underground Factory for the cost of 12 IPC.