Re air power:
1) dive bombers - good against tanks, trucks, ships and artillery type units
2) level bombers - deadly to infantry, especially in open terrain
3) torpedo bombers - good against ships
4) strategic bombers (and heavy artillery) - good against cities, resource hexes and fortifications
5) fighters - very good recon, good against bombers and other fighters. By default when you first create fighter units they are NOT set to intercept. You must turn this on if you wish your fighters to provide intercept of enemy planes. Even then, intercept is never a 100% certainty unless they are in the hex under attack.
Heavy artillery also good against ships and infantry.
Re RAW and OIL resources: your mobile forces depend on these resources. They'll be in short supply initially, especially in one town start games. Over time you will need to acquire more and use engineers to upgrade the ones you do have.
PPs: You need these to build units and purchase research. Again, initially they can be in short supply or you may have to be spending them more on unit creation than research purchases.
Supply: Gain an understanding of how it works. Very important!
ORIGINAL: towerbooks3192
Well I guess the best part is that it is not as daunting as Hearts of Iron 3.
I am getting used to grouping and regrouping units. I prefer to start stone age and I am a bit confused on what my units should be composed of and how I could attack and defend hexes (I know how to but I don't know when it is good to attack and if my units are good enough to attack the particular unit and what units to use in defense.).
I don't know how to mount an offensive though I think making a unit composed of at least 1 machine gun per 10 rifles(e.g 3MGs to 30 Rifles) is a good defense however I can't seem to get the right balance of an offensive unit.