The battle bunker is a simple combat structure which can house 5 soldiers who can fire from it, used by Soviets during War of the Three Powers.
Battle bunkers are simple, but useful buildings. Due to alterations in reality precipitating from the removal of Einstein from the timeline, these bunkers were no longer constructed through the Construction Yards. Instead, a Soviet Combat Engineer takes that role, having the tools to build one in a timely and cost-effective manner.
The new-era Battle Bunkers can still house five infantry units and does not consume power, but unlike the previous version it's smaller and all infantry units can garrison it. Since bunkers can only be made by Soviet Engineers, build radius is no longer a factor. This allows Soviet commanders to deploy it nearly anywhere, at the cost of being built by a vulnerable and slow infantry unit, who must recharge each time before building another Bunker.
Battle Bunkers are cost effective defenses and they have the potential to wreak havoc on any unit with the exception of artillery. However like all structures, they are useless when not occupied and the infantry inside are vulnerable to anti-garrison units such like Peacekeepers, Imperial Warriors and Conscripts, as well as protocols like Desolator Airstrike. Empty Bunkers can be taken over by enemies. In that case the original owner cannot sell it until it has been reclaimed.
The Battle Bunker is surprisingly fragile when faced with large groups and as with most other base defenses, artillery units can easily destroy it with impunity. Despite the fact that the Battle Bunker does not consume power, it can still be affected by the Allied Aircraft Carrier's Blackout Missile. This was likely done for balance reasons.