I called it, after some thoughts, Arnhem Chess, as it reminds me of battles in the second world war, fought not far from the place where I was born about a quarter of a century later, as it has a bridge that might be important but hard to take, and parachute troops. (I use the Dutch spelling of the name of the city.) The game is not meant in any way as a simulation of the battle; its name should be seen as a small tribute to those who fought to free my country.
Each player has the following pieces: a king, a queen, a rook, a bishop, a knight, a chancellor, and four Berolina pawns.
The game starts with players making secretly a deployment of their pieces. White must put his king, queen, rook, bishop, knight, and chancellor on the six squares of his first row, and his Berolina pawns on the second and third row. No pawn may be placed on the squares a3 and f3 (as they cannot move from there.) Black likewise must put his king, queen, rook, bishop, knight, and chancellor on the squares of the seventh row (his first row), and his Berolina pawns on the fifth and sixth row, but not on a5 or f5.
After both white and blacks setup are revealed, black is entitled to one reordering: he may either place one of his pawns on a different square (on the fifth or sixth row, not on a5 or f5), or have two of his pieces on his first row exchange positions.
So, for instance, when a black rook takes a white bishop on a3, and then white takes the black rook back, then a bishop is added to the reserves of black (the bishop changes color), but the black rook just is out of the game.
A player may, instead of making a normal move, drop a piece from his reserve on an empty square of the board. Pawns may only be dropped on one's own half of the board or onto the bridge (c4 or d4).
And, of course, there are more. Except for disallowing drops that give check or mate, I now think that the variants might be inferior to the main game.
Then, I asked myself: how should a variant on this board be? Crossing from one side to the other seems hard, and if we just add standard chess pieces to the setup, it might be too easy to come up with a defense strategy that doesn't give enough room for interesting attacks, hence allowing easy forcing of draws. The solution seemed to have the specific drop rule: as only pieces taken at the opponents side are added to the reserves, that rule favors attack above defense. Additionally, the chancellor is a strong piece that can jump over the `river' too. I considered quite some different pieces to add, but came to the conclusion that the current set is perhaps nicer than one with knightriders, rooks that can make non-capturing 1-step diagonal moves, or similar unusual pieces. The Berolina pawns solve the `corners' problem one encounters more often on boards that are not rectangles, and hopefully lead to less `congestions' on the bridge (i.e., pawns that just block each other.)
The free setup rule started when I didn't know a good setup myself, but I think it adds a little interest. At the last moment, I added the rule that black is allowed to make one reordering, as I fear that otherwise the advantage of white to start is too large.