In this operation, when you get rid of the enemy cruisers which are surrounding the convoy you're supposed to rescue, x2 BBs spawn to the north west, and x1 BB spawn to north/north east (these are the x3 BBs you need to sink to tick the secondary objective), followed by a large group of other ships that spawn to the north east.  That is what normally happens and that is what I have come to expect.   However, this evening, before the x3 BBs spawned, a completely different group of x3 BBs, including a Tier VIII Amagi spawned.  This completely thew me off.    Has anyone observed this before?  If so, do you by any chance know what triggers the spawn of these x3 extra BBs?