Question:
Suppose an air unit drops disrupted into a hex containing a port. May Axis naval units continue to use the port? If so, may Axis naval transports land ground units at the port? If so, may they then conduct the same sort of in-hex combat in the combat phase that airborne and amphibious units conduct?
Answer:
They may use the port there, but ground units may not be disembarked at the port. Rule 6 lists “In general, a unit may not enter a hex occupied by an enemy unit. Exceptions to this are covered in the appropriate rules.” Note that the naval transport rules do not list this as an exception.
Source:
Errata published at http://www.hmsgrd.com/Files/Europa/Second Front/Second Front.pdf

