so, in simple words, as if you talked to a dummy... what actually are theatres of operation? what define them? how do you recognize one when you meet it in the street?
haha - well, first off: fat ladies do not sing in Theatres in HOI3!
There are two parts to a Theatre in the game: an Area and an HQ.
First, the Theatre Area. This can be viewed by selecting the HQ button for the mapmode:
Germany starts with two Theatre Areas coloured blue and red:
- The blue area covers the western part of Germany, including the border with France that you are at war with.
- The red area covers the eastern part of Germany; East Prussia; and Slovakia. Slovakia is included because it is your puppet and you can conduct operations there the same as in provinces you control. The red area includes the border with the other country you are at war with - Poland.
The game allocates the Theatre Areas, you cannot define them yourself.
These areas are given names according to the names of the (sort of) historical Theatre HQs which have been defined in the game files. The blue area is called "OB West" and the red area "Oberk. der Wehrmacht".
The OB West Theatre HQ is located in Frankfurt am Main near the French border. The Oberk. der Wehrmacht Theatre HQ is located in Berlin. These are the two highest level HQs that Germany has.
At the start of the game you will normally find
all of the units within a Theatre Area are attached to the Theatre HQ located there, this includes any air and naval units which are based within the area. The HQ therefore has overall command of everything that goes on in this area, and in the countries beyond where we are at war with them, and the seas around it.
There must always be a Theatre HQ for every Theatre Area. For some countries there are none defined in the game files, so the game will create one for you. For Afghanistan the game might create a Theatre called "Kabul HQ". It will use names of major cities in the area.
At the simplest level, you can give AI Control to the OB West Theatre HQ and ask it to Defend against France; while you give AI Control to Oberk. der Wehrmacht Theatre HQ and ask it to Attack against Poland with the Objective to capture Warsaw. Each Theatre HQ will try to carry out its orders within its area, and only within its area. OB West will never send some of its units to fight in Poland, even if most of them are doing nothing.
You are in overall strategic command, only you can decide whether to move an Army from one Theatre to another.
As you advance into Poland (you are going to advance aren't you!), then the red Theatre Area advances to include all of the provinces your forces capture. Eventually, if you are successful and force Poland to surrender, then all of the provinces of Poland become German control (unless you have decided to sign the Molotov-Ribbentrop Pact) and the red Theatre Area will cover all these provinces.
Now the game might decide, since you are no longer at war on your eastern front that it no longer requires the red Theatre Area, and it will want to merge the two Theatres into one, so that most of your forces might be sent to fight on the western front against France and its Allies. But the game will not merge the Theatres unless you allow it to do so. To do this go to the Production Screen and select Define Theatres. Nothing may happen if the game decides that it is not a good time to merge the Theatres, you cannot make it.
On the other hand, if you decide to declare war on Denmark, then you will probably find that it will want to create a new Theatre Area covering northern Germany and including the new front with Denmark. If you let it, then it will probably create a brand new Theatre HQ for you, which might be called "Hamburg HQ". If you place an Army in this Area ready to invade Denmark which is not already attached to any Theatre and click on the "Theatre Forces" button on the Production Screen, then you should find that the AI will attach the Army to the Hamburg HQ for you. You can also do this yourself manually. You can then give AI Control to the Hamburg HQ and give it an Attacking stance with the Objective Copenhagen, and it will use that Army to invade. You might also want to give the new Theatre HQ control of some air units and even a few fleets.
You decide what forces your Theatre will use. It will advise you what it thinks it needs, and even ask you to build extra units, but it cannot force you to give them. If you decide that the Hamburg HQ really doesn't need some TAC bomber wings, then don't give it to them. Leave the TAC's with OB West to use against France.