The battle bunker is a simple combat structure which can hide 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 time and cost-effective manner.
The new-era Battle Bunkers can still house five infantry units, but not only conscripts, any infantry unit can take advantage of its sturdiness, and also take only one "building tile" of space. While retaining the excellent characteristics for durability and zero energy consumption, since they're built by using special ability of Soviet Engineers, "build radius" is no longer a factor, thus allowing Soviet commanders to quickly set up makeshift defense mechanisms around and away from forward bases.
Battle Bunkers are useful all-purpose substitution to other defense structures, provided with correct combination of occupants. However like all structures can be garrisoned, infantries inside are vulnerable to anti-garrison units such like Peacekeepers, Imperial Warriors and rogue Conscripts, as well as protocols with anti-garrison effects (Desolator Airstrike and its variants in this case, although they're Soviet protocols). Once it's cleared of infantry, enemies can take it over for their own. In that case the commander cannot sell it until it has been reclaimed, as that would be unfair.
Artillery units also can demolish Battle Bunkers with impunity. Strangely, Allied Aircraft Carrier's Blackout Missile can disable a Battle Bunker, despite its lack of a draw of electricity, this suggests that each Battle Bunker has a internal generator to supply necessary power for being functional.