I devoted much of the intro to my Baltic invasion scenario to how to keep the preparations secret in order to catch NATO off-guard. I chose an extreme form of compartmentalization; lock up a small planning staff and isolate it from the outside world entirely.
The typical day-to-day routine of secrecy is very different; it's about compartmentalizing secret information. A general security clearance doesn't suffice to learn certain secrets; you need to be in a list of authorized personnel who were chosen because they need to know the secret. This often runs into the problem of inflation; the lists of authorized personnel keep growing. It's also troublesome because often times someone who needs the information isn't on the list, and efforts may be duplicated without anyone noticing.
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Now think about the current sunny times between Erdogan and Putin, and his crackdown on the Turkish military and replacement of much of its leadership.
I'm not much concerned about this in itself (though the unlikely case of Turkey leaving NATO would create quite a deterrence & defence challenge for the Mediterranean NATO members, then approx. justifying their present naval expenditures).
But what about SHAPE (ACO)? How trustworthy are Turkish officers in NATO staffs, would they be excluded from viewing or even contributing to defence planning concerning the Baltic states or Poland? Judging this individually wouldn't help to dodge the problem because a successor might be offended by not getting the same access as his more trusted predecessor, for example.
What if Turkish officers will be excluded and the AKP politicians don't keep this confidential, but protest loudly? Would the Turks suddenly not consider themselves as true NATO members any more because NATO seemingly reduced them to 2nd class?
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It seems to me as if there's quite some demand for diplomacy in this case.
My approach would be to focus all high-ranking Turkish officers in SHAPE on various NATO plans regarding the surroundings of Turkey as an excuse for not assigning any to Baltic defence plans (which also means that Turkey wouldn't do anything for Baltic defence according to those plans). The development of the various Turkey-centric contingency pans would need to be published in Turkey (loudly) to establish this excuse in advance of troubles.