gistfile1.txt

         +-------+-------+
         |       |       |
         |  A1-> | <-B   |
         |       |       |
         +-------+-------+
         |   ^   |       |
         |  A2   |       |
         |       |       |
         +-------+-------+

The rules are:

  * For all units that are moving *at* each other (A1 and B in the
    example), fight them and kill the loser(s).
  * Move all remaining units.
  * Fight any units that are on the same square.

In this example:

  1. A1 and B fight.
     If A1 wins:
       2. A1 moves to B's former location and A2 moves to A1's former
          location.
     If B wins:
       2. A2 and B both move to A1's former location and fight there.