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This page is written by the game's inventor, Ralph Betza.

Doublestep Chess and Doubletime Chess

In Doublestep Chess, the privilege of making a doublemove is no longer limited to unmoved Pawns; instead, all pieces may make doublemoves.

Although Doublestep Chess changes just one rule, there are several paragraphs discussing the rules because of the surprising implications of this single change.

Doubletime Chess intereprets the rule of doublemoves differently, with more surprising implications.

The Rule of Doublestep Chess

The rules of Chess apply except as follows, except as follows, except as follows, yes, we've heard that refrain before and it's everybody's favorite, isn't it?

In Doublestep Chess, everybody can make a doublemove, not just unmoved Pawns.

To make a doublemove, a piece makes a non-capturing move, and then it makes another. For example, 1. Nb1-c3-e4 is a legal doublemove.

You'll notice that when a Pawn makes a doublemove, both the moves must be in the same direction, because in fact a Pawn can only move in one direction without capturing; but the FIDE rules do not prohibit other types of pieces from changing direction when they take their doublemoves.

Doublestep Chess may sound like a game that belongs in Limited Doublemove Chess, but in fact Doublestep is a single-move game in which the pieces make doublemoves, not a doublemove game in which both moves must be made by the same piece. There is a big difference, as the next section shows.

Doublestep is Unfair, Says FIDE

The rules of FIDE Chess declare that doublestepping is unfair at least in certain cases when a doublestepping piece evades a singlestep attack and then lands safely with its second pace. To remedy this fault, savants[1] have made the rule of en passant.

According to the rules of Fide Chess, when the first move of a doublestepping piece lands on a square attacked by the foe, the doublestepper can be captured en passant: the capture is performed by as though the second step had not been taken.

Doublestep Chess follows the rules of FIDE Chess, and allows all pieces to be taken en passant if they make doublemoves; but please notice that only a singlestep move may be used to perform an en passant capture.

In FIDE Chess, only Pawns and Kings can be taken en passant, but that is because only Pawns and Kings have any sort of doublemove.

(Notice that Castling is already a special doublemove, and so in Doublestep Chess you may not play O-O-O and Kc1-b1 all in the same move; since Castling is a doublemove of sorts, in FIDE Chess you may not play O-O-O with d1 attacked lest your King be taken en passant.)

Mum's the Word

It should not be necessary to specify that the normal double step of a Pawn already counts as a doublemove, and so in Doublestep Chess you may not play e2-e4-e5 all in one move.

You should be aware that the move e3-e4-e5 is a legal doublemove.

Zero is not Two

If the second part of a doublemove returns to the starting square, you have made a null move. However, the rules of Chess emphatically state that you must move! Therefore, the null move is not permitted.

Doubletime Chess

Doubletime Chess allows the second part of a doublemove to be a capturing move. As a result, 1. Nb1-c3-e4?? appears to give check.

The first part of a doublemove must, as always, be a non-capturing move.

Doubletime Legalism

When an en passant capture is made, the piece that is being captured is taken on the square where it made the first step of its doublemove, and thus the situation is as if the captured piece naver reached its intended destination.

Clearly, the rules of FIDE Chess require that if the second part of a doublemove was a capture, then making an en passant capture in response uncaptures the originally captured piece and makes the wronged party whole. (The piece that appeared to have been captured was in fact just held hostage.)

For example, after 1. Nb1-c3-e4? a7-a6? 2. Ne4-f6xe8 Ng8xf6 en passant, the Black King reappears on e8, safe and sound. Although this result may seem a bit odd at first glance, careful calm consideration will convince you that no other result is possible under the standard laws of Chess.

Doubletime Special Case

After 1. Nb1-c3-e4? a7-a6? 2. Ne4-f6xe8 Ng8xf6e.p., it is as though the Ke8 had never been captured. However, after 99. Re6-e8xd8, the reply Kd8xe8 en passant is not legal. The Kd8 has been removed from the board, is being held hostage, and is in no position to effect his own rescue!

Doubletime K+P versus K Endgame

With White Ke1 and Pe2, versus Black Ke8, the game proceeds:

1. Ke1-d2-d3, Ke8-d7-d6 2. e2-e3-e4+, Kd6-e6 3. Kd3-c4+!

Now Ke6-d5xc4 is not legal because of e4xd5 en passant.

3. ... Ke6-d7 4. e4-e5-e6+ (e4-e5+ is simpler) Kd7-e7 5. Kc4-d4 Ke7-e8 6. Kd4-d5-c6+! (Kd4-e5 would be stalemate).

This simple endgame demonstrates how the doublemoves and en passant work together.

Doubletime K+R versus K Endgame

With White to play, you can put the pieces almost anywhere, the position is already checkmate.

This simple endgame illustrates a major characteristic of Doubletime Chess: as soon as the position opens up, Rooks become incredibly powerful. En Passant works only when the first step of the doublemove lands on a square you attack; against Rh1-e1xe8, control of e7 is no help at all.

Games of Doubletime Chess will often be short, and the computational burden will be great: you must think hard before opening the position or allowing it to be opened. I used to like this sort of game when I was younger, but now I prefer a simpler game -- the tactics of FIDE Chess are as complex as I like, and I feel that more complex tactics take something away from the strategy of the game.

However, I used to like this sort of thing, and you might like it now.

Which is Better?

Doublestep represents the maximum in the elegance of its design: only one rule is changed, and that one small change completely changes the game. Compared to the 1970s game of En Passant Chess, Doublestep is not only more elegant but also offers better play (e.p. Chess favored the defense too much, but Doublestep balances offensive doublemoves with defensive en passant captures).

Doubletime changes two rules, but always in the direction of greater freedom of choice. We all love freedom; I think everybody in the world should be free to agree with me.

How can one not like a game in which pieces that have apparently been captured may in fact have not been captured at all? And the balance between offense and defense, is it not wonderful how it is maintained by the possibility of en passant captures freeing the hostages?

I cast my vote for Doubletime Chess, but I'd rather play Doublestep Chess because I feel the tactics in Doubletime are too intense for me.

I first read this explanation of en passant in Philidor, a savant if ever there was one.