The scenario is this:
On Round 3, Japan moved two destroyers into sea zone 25 on its turn.
Then, after that but also on round 3, the U.S. moved a destroyer into SZ 25 as well as a noncombat move since Japan and the U.S. were not yet at war. During the Collect Income phase of this U.S. turn, however, they are finally able to declare war on Japan and they do so.
On Round 4, Japan moves a battleship, 3 cruisers and 2 subs from SZ 6 to SZ 25 to conduct combat on the U.S. destroyer. The two Japanese destroyers from the Round 3 noncombat move are still in SZ 25, but the Japanese player decides they are not going to be part of the combat in the sea zone.
Then, after the Conduct Combat phase is completed, Japan then moves those two destroyers that did not make a combat move and were not involved in the conduct combat phase and they make a noncombat move out of SZ 25 and move to another sea zone.
So, is this allowed?
Can the attacking power, in this case Japan, choose which sea units to will attack in the SZ 25 battle? Particularly since the 2 destroyers that moved in SZ 25 did so during the noncombat move of the previous round and the rules stipulate that if a non-hostile SZ becomes hostile â€“ which usually happens because of new ships being deployed by a power with which youâ€re at war â€“ the sea units in that sea zone have the option of leaving the sea zone.