ChadChad is the result of an exercise in mimimalism. The question that triggered it was:
"How much is actually needed to make a chess variant?"
Obviously it requires a king. Obviously 'pieces' wouldn't be considered an excessive feature either, but pawns? Why pawns. No pawns.

And different pieces? There's the king of course, but why different pieces. No different pieces. Nor mutual capture of pieces for that matter. Chess is about capturing the king, not slaughtering an army. So I gave the king the traditional move, provisionally, and chose rooks as the most logical pieces on a square board.
Now what?

It was soon established that a king in the corner with two orthogonally adjacent rooks constituted an impenetrable fortress, which left nothing else for the remaining rooks to do than strolling about aimlessly and having tea. It eventually became clear that without mutual capture of pieces, the game wasn't going anywhere. But having rooks slaughter one another all over the place, with mutual impotence as the most likely outcome, wasn't too tempting either.

The Wall
The solution that eventually emerged was the 'Wall', the twelve squares you can see around each castle in the diagram. It serves to restrict mutual capture of pieces to one specific condition: the mutual right to capture exists only between an attacker on the wall and a defender inside the castle. That in turn begged for promotion of an attacker that actually managed to enter the castle, and that in turn begged for a more flexible king, leading to the additional knights move.

Chad became very popular at the games club Fanaat of the University of Twente, with two top players demonstrating convincingly that it showed no lack of finesse.
As an exercise in minimalism it was ironically overtaken by Shakti, a chess variant that unintentionally happened some time later. It doesn't make Chad any less of a great game.

Chad © MindSports
Java applet © Ed van Zon