Historical Question - Assault Gun vs. Tank

[Erik]

Alright military-types.

Question - other than a rotating turret, what is the difference between an assault gun (think StuG III) and a tank (Pkw. IV, for example)?

When would one be more desirable than the other?

All I can figure out from reading is that the assault guns were generally larger guns than the tank main gun but this changed over time (e.g. StuG III had 75 mm but the Tiger had 88 mm on a turret).

And couldn't any type of ammunition be put in any kind of main gun? So HEAP, Sabot, HE, whatever, be fired from either type of vehicle?

[David Craik]

An 'assault gun' like the Sturmgeschütz III is a self-propelled artillery piece, cheaper and quicker to produce than an equivalent tank and best suited for siege against fortified targets or in a mostly static defensive role against tanks. As an aside, the Germans used anti-aircraft guns against enemy tanks in a similar manner as well to great effect. A tank is most effectively used in a manner similar to cavalry where terrain permits (Guderian, Rommel, Mellenthin, et al). Due to their static turret, a mobile artillery unit would be extremely ill-advised to 'take the field' against a tank unit, it would be like shooting fish in a barrel, easily outflanked and enveloped.

So the difference as I see it would be a case of economy, time, capability, and tactical thought. A unit of these assault guns (though very effective when used within their role, their low profile made them extremely difficult to hit, espescially when dug in) would be a joke if one attempted to use them like tanks, and although one could use tanks as mobile arty this would be a huge waste of their capability and expensive - like using a cavalry regiment as packhorses or for guard duty. The French apparently used tanks like this quite a bit..guided by WW I type thinking - static engagement, and thus though their tanks were actually very good they for all intents and purposes threw them away by considering them little more than cannons which didn't need to be towed or parcelling them out piecemeal in infantry support roles.

There is also a Tiger variant - the Sturmtiger - that was an assault gun - 380 mm.

Of the tanks and light artillery pieces I know, all types of projectiles could be used in either one.

[Erik]

So the turret and price are the key variables.

No turret = cheaper but it also means that the AG is better when dug in and not moving. Ideal against static targets, like pillboxes, buildings, troops not moving around, etc.

Useful as tank hunters if they can get the drop on the enemy tank by coming from the right direction and correctly predicting the tank will enter their field of fire.

With a turret = more expensive but also faster at turning around and shooting. Good against what the AG is good for but also for other, more difficult targets such as things that move (trucks, tanks, troops).

Can find a ditch, dig in, and still engage 360 degrees, so more flexible.

Did I get that right?

[David Craik]

In general, Erik. Specific pros/cons and variables would depend on the pieces compared. The lack of turret also allowed various AGs to mount a larger gun than a tank of equivalent size due to extra space (no turret drive mechanism) and the increased strength of a solid mount.

Then you had weird hybrids, such as the KV2 'artillery tank'. Sticks out like a sore thumb, has a moveable turret, and packed a 152mm howitzer.

Though some armies fielded things that should have been used as mobile artillery in a 'tank' role, and some used tanks as artillery; they should really be considered rather different animals. Not quite apples and oranges, but maybe grapefruits and oranges.