Just to clarify... this base wasn't exactly undefended at first, but the few defenders where quickly overhwelmed. But as you can see all hangars were dropped, which of course immeadiatly changed the balance. BTW, this particular Bish attack was no NOE or CV raid. They upped ~ 2 sectors away and were causing a full darbar all the time.
Both the rook attack on 65 as well as this Bish attack on 66 happened at the same time. It was a quite dynamic situation in a 3-4 sector area, a multi-sector battlefield. And that was a good thing with lots of fun and yelling armchair generals.
It had been earlier that eveining when Bish run a handfull of NOE missions including repeatedly aborting the attack when meeting resistance and quickly hitting elsewhere on the map.