Submarine availability?

Originally Posted by RWingfield

Sorry if it's a basic question, but how do I join the 2nd flotilla? Time on my career is Jan 1940, and admittedly, I'd like to get the IXB. Only flotillas to appear on my transfer list are 1st and 7th (current). Also, just running vanilla SH3.

After your base is moved to France, 2. Flotilla will be available, for an unmodded game.

Beery's Flotills Mod will allow you to start with 2. Flotilla in september 1939.
If you like IXs, I reccommend it.