the meaning of German "A op" abbreviation

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Hello,

What is the meaning of "A op" in the following sentence for Marinegruppenkommando Nord KTB:

"... und durch A op Gruppe Nord persönlich mit mündlichen Erläuterungen ... übergeben"

?

A op = Operationschef ?
A op = Operationsabteilung ?
... or is it something else...?

Many thanks ahead of time!

Nikolai

[Klabautermann]

I guess it means "Admiralstabsoffizier operativ"