So - yes - and I will clarify in the rules.
A very common tactic in our games is to send planes on an early chit draw to attack ships in port. When the ships move out of port, the planes execute their snap fire with a -2 modifier. Often, the initiative player will not only send planes in to attack ships in port, but also move his navy into the sea zone outside of the port. When the defending ships sortie, there is the one round of air snap fire at -2 and then you would execute a naval combat when the ships come out of port and engage the blockading navy.
If the defending ships do not want to face the blockading ships, they would have to sit in port and suffer 4 rounds of -2 bombing (or hope they turn away the aircraft with AA fire).
Think Taranto Raid here. On the first chit draw, the British could move their carrier next to the sea zone containing the Italian fleet at Taranto and fly a swordfish off their carrier into the sea zone/port. If the Italian fleet leaves port, the swordfish would execute its snap fire (with a -2 DRM. . .and Cunningham's naval air re-roll) and bomb the Italian battleship. If the Italians do not move their fleet, the swordfish would still get to execute it's port attack on the combat phase after movement is over.
Pearl Harbor works the same way. After one round of port attack (with a -3 drm (-1 for surprise attack and -2 for attacking ships in port), the US navy can retreat into the sea zone out of the port and end the combat.
clear?
