I guess it could be useful to add an explanation of how the game handles the fact that the same scenario works for both stand-alone use (play scenario) and as part of a campaign.
This because the above
Kerensky wrote:Open the individual scenario (that is the start of a campaign, such as Kursk) in the editor, and pick up and place units there. When starting a new campaign, you will see the units you placed, and they will, if marked as core, will be your core units that you carry on as you continue that campaign.
...is
only true for a scenario that starts a campaign!
When you start a scenario (load up a map for a single non-campaign play) you get what you see (in the editor) - if you change around the units, that will affect what you start the scenario with. And this is equally true for a scenario that starts off a campaign too.
But when you play that scenario as part of an ongoing campaign (i.e. not the first scenario in that campaign), "getting what you see" is only true for auxiliary units, or more specifically
units not placed in hexes marked as deployment hexes.
(The editor symbol for a "deployment hex" is a small green or grey tank or plane with an arrow pointing down underneath)
Meaning that any unit placed in a deployment hex will be removed when that scenario is played as a campaign. Instead that hex will be empty and available for deploying the core you've brought along from any previous campaign scenario(s).
This means:
To make meaningful changes to scenarios when played as part of a campaign, make sure the unit isn't placed in a deployment hex (or make sure you remove the deployment symbol for that hex).
You will find that most preplaced units in hexes designated as deployment hexes are marked as core units, and conversely, that most preplaced units in hexes outside the deployment hexes are marked as auxiliary units. Why? Because this is what makes basic sense - any preplaced core unit is generally supposed to vanish when you bring your own core along; and any preplaced auxilary unit is generally supposed to be present regardless of whether you're playing the scenario as a stand-alone or as part of a campaign.
Let me spell the four possibilities out in detail.
First the two most common cases:
Core Unit, Deployment Hex: Unit pre-chosen for you as a stand-alone scenario; unit not present in campaign play but hex available to deploy your own core.
Aux Unit, Not a deployment hex: Unit available for your use during this scenario only (regardless of whether it is played stand-alone or part of campaign)
Then the two uncommon (but perfectly legitimate) cases:
Core Unit, Not a deployment hex: Unit pre-chosen for you in all cases, and what's more: since it is a core unit, it will travel with you to the next scenario of a campaign (all core units are equal). Thus, you have just been gifted a unit for free! This is used by DLC campaigns to steer your selections in certain directions. For instance, there's a Afrika Korps scenario where you can gain Italian self-propelled artillery to your core. Thus, if you see a scenario and go "I would have wanted that unit to be given to me for the remainder of the campaign" you simply have to change it from Aux to Core in the editor (and make sure it isn't placed in a deployment hex).
Aux Unit, Deployment Hex: Unit available for your use as a stand-alone scenario only (during campaign play the hex will be emptied and available to deploy in). Why would you do this? I don't know, perhaps to give you reinforcements you only need when given crappy prechosen "historic" units for single-scenario play...
Hope this helps