My two pennies worth of tactics is more specific to airpower.
German Air Tactics.
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Depending on the rules which have been agreed. I tend to place DBs, FBs & F's in Front Line HQ especially the Panzer Armies. Bombers tend to go other HQ's. The way I see the Panzer Armies is that they do the bulk of the fighting and need close ground support of the DB's & other ground attack planes.
Typically when playing against another Human (Soviet), as I'm finding out, they tend to withdraw all airforces for retraining, reequiping and building up pools for their Winter Offensive.
Airfield Attack at the start of every turn, every HQ you can reach, to ensure the sneeky Soviets haven't transferred up AirGroups during their turn.
You'll have to decide whether to concentrate units for better protection or spread out your air units to reach more area of the map.
If your opponent has withdrawn all planes to Siberia the following situation occurs. Apart from smashing as much of the Soviet Airforce on Turn 1, after this, typically the only targets left are entrenched Soviet Armies and Cities.
As cities get into range of the Long Range Bombers, Moscow, Leningrad, Stalingrad and Oil Productiong centers in the Caucasus need to be targeted. Vary your targets as much as possible only deliver sustained bombing on Primary Objective Cities. You shouldn't see much of the Russian Fighters until September, they should still have fairly low experience by this time. So expect some casualties. As winter '41 approaches, the Soviet Airforce will be stronger, more experienced, so only bomb targets with fighter escorts.
In Winter prepare to use planes for Air Lift Operations.
Remember, as the Germans in '41, you can use air units fairly recklessly as they won't experience too many losses.
Soviet Air Tactics.
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Here you have to use common sense. You need to prepare for the coming Winter '41 Offensive (build up the replacements pool and train air units) and also to inflict damage to the Germans where ever and when ever you can.
There's not much that you can do about Turn 1. But there's a few strategies you can employ to annoy the nasty Huns.
1) For the Turns 1-6 Panzer Korps will go out off range of air cover from their parent HQ's. Use air units to hit them. Disrupt them, annoy them, you may cause some damage, receive some losses, in the Grand Scheme of things as Soviets can survive these losses. There are several benefits a) You annoy your opponent, by forcing them to painstakingly try to air attack every HQ you have in range, every turn. b) You cause some amount of disruption to PzKorps, losses even. c) Depending what you've done, you may force the German player to re-deploy other air units from other sectors.
2) Start training about 4/5ths of your available units. This will let the units recover in strength and increase experience.
3) Use the other 1/5th in Guerilla air tactics. You need to use these units in force in one area. Yes these units will receive losses when they fight but also gain experience. I believe this experience is more than received from Training.
a) Until the main German air units start coming into range of Leninggrad. Use air units to nobble the Finnish Air Force. Rotate air units every turn with those receiving training. This gives units combat experience and a chance to recouperate. When the Germans start getting in range, you might be lucky that some air units may hold their own. But I'd be tempted to withdraw them to another area or Siberia.
b) Employ the Air Units in Sectors where there is no air cover from the German parent HQ. Ideally place them in HQ's with are under direct assault from Pz Korps as planes will be used in ground combat resolution. Typically the Pz Korps will be far ahead of their HQ's for Turns 1-6.
c) Place Air Units to be used in Ground Combat resolution in areas that need desperate defending. Kiev and various cities on the road to Moscow. Give the Germans grief & annoyance, coz they're giving it too you.
4) From September, start using Air Units in the defence of the approach to Moscow. Bomb German Airfields, the Soviets should now have sufficient to make attacks successful.
5) Give key industrial/oil cities air cover from the start, stop the German terror bomb tactics or at least give unescorted German sorties casaulties. I use 2 strong fighter units where possible. Each turn alternate each of these 2 units between training and CAP.
6) You need to damage the German Airforce numbers, especially the Bombers/DB's. Produce fighters with good cannon ratings, these will take out the bombers more easily.
7) Use a fairly well trained long range bomber, to attack Ploesti, every so often from HQ's in the Caucasus.
8) Wait patiently until Winter '41 and help the Germans keep warm in their beds by bombing them
9) In Winter '41, the Germans will usually employ the City fortress tactic and not hold a continuous front. The German player will have to use Air Lift operations alot to keep the readiness of Units high. Use HQ's with fighters on CAP.
10) Airbase Attack every German HQ you can at the start of every turn.
Well that's my take on using air power for both sides.