Yeah it's a sneaky one that, you'd think they'd add a tool tip. But until they do...

Hey - I created a flying only channel - so people could have less notifications for games they didn't want. Look for Internet Flight Rules - here on youtube - thats me, be great to have you there!

I'm glad you took something away from it. To answer your question, supply is extremely important. Sometimes you will need to put down supply lines (port / rail / hub) but sometimes this isn't always practical. Remember it's better to have an army half as strong that's fully supplied and equipped, than the other way round - sometimes less is more. Also ensure supply for the general is truck 3, and use transport aircraft for supply drops as well (they can really help tip the balance in some situations). Definitely set your generals to fight aggressive in the lower supply areas, so you can ideally pass through them as quickly as possible... Don't forget sometimes, it can be more effective to retreat back, closer to your supply lines, lure the enemy across, and then with him under the same poor conditions you just were, use your tanks to try encircling some of his units.... As for stuff getting handed over to allies after the fight, this is frustrating. Basically, if the allies already lay claim to certain areas (ie Italy wants Ethiopia) and you say as Germany fight in this area, Italy will get it back, but then as you help Ethiopian lines get pushed even further out, the territory basically falls into their hands too. The only way I find around this, is to invade territory by not using any of the existing land controlled by your allies - this also happens in reverse, for example if you were Germany and were invading Poland, but somehow Italy did almost all the work, the territory would fall over to you. Only when there's post war agreements over who gets what, does it get divided up according to who contributed the most fighting. Hope this helps

Thanks a lot of these explanations. I didn't think the supply crates was this essential. The weird part is that the AI doesn't seem to care to build up any of them in the contries they control, so I have to build them straining my build que. Now I will try to build some kind of mesh of railway to supplies so they can't be cut of so easy. @@gameswithbrains

Maybe it's a DLC things, but you can ask for controll of territory in the diplomatic window. If they have cores or claims they will probably refuse, but the option is there.

The issue you are facing is nothing to do with harbour size, that's more to go with supply stats - I should have been more clear. The issue you are facing is everything to do with a limit imposed by the game depending on what level of tech you have unlocked (navy invasion wise). At level 1, you are limited to 10 divisions total. If you try plan for more, that pesky message appears as you have described. I think it be more helpful if they just greyed out the ability to plan more, with a tooltip explaining why. I guess they allowed it, so that naval invasion can be queued up, I don't know.