Tank Destroyer is a mission. The first one's in the US Army were simply 75mm guns mounted in the bed of an M2 Halftrack. The TD battalions learned in North Africa that these were unsuitable as what they really needed was a high velocity cannon. Those were tough to fit inside the fledgling Sherman Tanks, and so needed a new turret. What they came up with was and up-armored Sherman with a roof-less turret.
The Germans also had a simple solution: they took obsolete tank chassis and built a heavier gun into a casemate -- no turret. If you needed to train the gun more than a few degrees, you had to point the entire track at the target.
“The Germans also had a simple solution... you had to point the entire track at the target.”
That’s fascinating. Because a dual tracked vehicle can turn in place, verra easily. It would require more coordination between the driver and the gunner but I can imagine it was cheap and devastating. Lotta bang for the buck, as they say.