Historical convoy and task force movements
 

I noticed something when starting a campaign out of Manila in an S-14 class boat. I ended up patrolling around the north and northwest coasts of Luzon and found huge Japanese task forces of mostly troop ships, escorted by a light cruiser and a few destroyers, massing around those areas, as well as a Kongo class battleship group sailing down the west coast. In my next patrol, out of Surabaya, I saw a similar massing on the south coast of Mindanao.

This fits very well with the Japanese assault on the Philippines which was occurring during this time. I really like the actual in-game realities reflecting the historical realities. It adds a lot to immersion.