Ramming

When one ship (in battle nav) attempts to move into the square that another ship is occupying, the other ship is rammed and both ships suffer damage. If the ramming ship is larger than the ship being rammed, the smaller ship is "pushed" out of the square and suffers more damage than the larger ship.

Historical Note
Prior to the blockade release, there was no such thing as ramming. The swordfight began when both ships occupied the same square on the battle navigation board.