Starting in the 1944 Italian campaign, the Allies started to increasingly bump into German Panther turrets mounted on top of buried concrete bunkers, rather than atop tanks, for which they were increasingly running short of fuel.
It actually wasn’t a new idea, as the French had used scores of old FT-17 and newer Char turrets on the Maginot wall and other places.
These instant defensive fortifications were usually sited to cover choke points, and being low to the ground was difficult to spot or knock out.
The buried concrete bunkers include a generator for power, large supplies of ammunition – much more than a tank could carry – and protected living quarters for the abbreviated turret crew.
The Japanese were also users of the concept in WWII, especially in remote garrisons where gasoline was hard to get after 1942 and a dug-in tank could still be a “muzukashi” hardpoint.
These concepts outlasted the War, especially in Eastern Europe.
The Finns even bought 56 surplus T-55 tank turrets (just the turrets, which left the Soviets scratching their heads) in the late 1960s in what was likely the last use of such an idea. They placed them, coated with an asbestos-cork mixture to prevent moisture, along their craggy seacoast as the 100 56 TK (“100 mm, 56 length caliber, turret gun”) system, which was operational as late as 2012. These were arranged in 14 “sea fortresses,” each one equipped with 4 such turrets, linked by a central command and control and spotting system.
And of course, they were used extensively in the Middle East:
The go-to book for more information on these (even covering Albanian and Bulgarian cold war panzer and T-34 turrets) is Neil Shorts’s aptly named Tank Turret Fortifications.