I recall that SH3 had some defences against port attack - not total and not everywhere, but some, so suprised that SH4 does not match that. Subs did not raid ports in the war BECAUSE of the protection I assume - otherwise they would surely have seized the opportunity; hard not to. As you say, 'unrealistic' - but it all helps the reward and it is something to do when you just can't find that shipping lane....
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