The anatomy of the forced draw

The work on this project led to a few rather simple insights about forced draws in general. They can only occur in four situations:

  1. Two targets can be attacked and there is only one defender. In this case the defender can be overloaded to reach a perpetual.
  2. Attacks that result in a situation where the attacker is left with insufficient forces (just a queen) to either mate or win material.
  3. Retreat squares are cut off, so an attacked piece cannot escape.
  4. The players are sick of it and want to join the bar.