Talk:Christmas 2013 Event/@comment-111.109.137.130-20131224043609

So... this is the quest needed to unlock E-1:

謎の潜水艦 "イオナ" と接触せよ! 敵潜水艦を捕捉, これを複数撃滅し, 謎の潜水艦 "イオナ" との接触を図れ!

I'm reading that as go kill some subs. Problem, the forums and this place recommend 4-1. But I've only unlocked up to 1-3. What is the earliest map that has subs and what is the minimum fleet needed to get that far? All Heavy Crusiers?