In the second campaign, I get an airplane unit. When I move this unit, it drops supply troops. What are these used for? In battle they're just fodder, and I can't see any use for them on the campaign map other than taking up space.
Move platoons to the neighboring (with a warehouse) cells, they automatically are charged with ammunition and fuel.
I also have had a few spotter units. In the tactical battles, they have no option to call in artillery. The only units I've seen so far who can call in artillery are platoon leader squads. Never a spotter. What are spotters used for if they can't call anything in?
Artillery observers available in reserve pool, (in some operations they directly in the active part of troops). You can change the any type of support squad (like ATR or MG) on them on first turn.
But commanders also have the opportunity to direct artillery support.
Is there a way to tell a tank to use HE shells to attack an area? I've been able to issue an area attack are order, but they seem to be firing mainly MG and every once in a while an AP shell, even thought there is no armor in the area.
Attack order - it's a order for _movement_ but in a special way, not by firing. To control the fire use orders: set sector, set priority targets and firing with correction.
Choose a tank platoon leader and use the command to fire with the correction (very similar to the guidance of off-map artillery) - tank platoon will be shooting at the intended target by HE and shrapnel rounds at first.
Tanks at WWII period did not have stabilizers and if you send them into battle, then they will be in motion to shoot the main gun with only small distances, preferring automatic weapons such as machine guns.
APHE projectiles used against infantry, if no other ammunition. Some tanks do not have high-explosive ammunition at all (like UK made MkIII and MkII tanks).
Finally, is there english documentation that explains what all the different weapons, grenades and ammo types are?
Specific documentation for a description of ammunition will not be. Although work on the translation of the full manual in progress.
Impact munitions vs armor can be viewed using the in-game diagrams of armor penetration.
I had a regular russian infantry unit holed up in a building, and out of the woodline came some germans. My squad in the building opened up with heavy machine gun fire, even though they weren't an MG unit. I hovered the mouse over their ammo, and I only recognized two of the four gun types they were carrying (Psh and rifle, neither of which are HMG). It would be very helpful to know what kind of guns my squad has. Also, what types of grenades and what their ranges are in case I want to use them to take out light armor.
Grenades thrown at a distance of 30 meters for anti-personnel (RGD-33, M24 and Molotov's) and 10-15 meters for anti-tank (RPG-40, HHl-3, 6xM24).
Every infantry squad has a LMG, MG-34 is for the Germans and the DP-27 for the USSR.
HMGs divided into separate squads marked with the icon. For Germans, it is MG-42, and for the USSR is Maxim and DShK.