Slitherine

Ok so I installed base game Panzer Corps 2 then installed the update 10506 then if I buy an Axis Operation such as Spain or 1939 ... I then install these but then do I have to reinstall the latest update again ???

Do the axis operations overwrite any updated files ???

The easiest solution is to get a key for Steam and let it do the rest for you, also solves any installation problems in the future.

If you install the base game with the latest update all the DLCs are included.
They are just not authorized.
Installing a DLC just adds the authorization for the DLC.
For Steam that is what happens.

For Slitherline it acts like it is doing a full install [time wise].
Why it acts this way and what it is doing is not clear.

So simple with Steam, not to think, just to activate the game or dlc.