Which Chess960 position gives the most first moves?

Sixty-two positions give White 21 legal first moves, the maximum. Sixteen are always pawn moves, four come from two knights standing off the rim, and the twenty-first is castling, which is legal at once when the king and its rook already stand on c1 and d1 or on f1 and g1. Position 81 is one of them. The standard array gives 20.

Which Chess960 position gives the fewest first moves?

Twenty-two positions give White 18 legal first moves. All of them have a knight on a1 and a knight on h1, where a knight reaches one empty square instead of two, and none of them allows castling on move one. Position 310 and position 366 are two of the twenty-two.

How many Chess960 positions start with an undefended pawn?

In 600 of the 960 positions at least one pawn on the second rank has no defender at all, and in 144 of those two pawns do. The corner pawns are the usual victims: a2 is undefended in 228 positions and h2 in 228, against 32 each for d2 and e2.

The best Chess960 positions, by properties you can count

Q: Is there a best Chess960 starting position?

Not officially, and not by any settled measure. Both players get the same eight pieces on the same eight files, so no arrangement gives White a resource Black does not have a move later. Engine evaluations of the starting arrays exist, but they are small, sensitive to depth and settings, and disagree with each other, so this page sorts the positions by properties that can be counted instead.

Nobody has crowned one of the 960. What can be done is to sort them by things that are true of the arrangement itself, which is what this page does, position numbers included.

By Carl Brodsky

Is there a best Chess960 starting position?

Not in any official sense, and not in a settled unofficial one either. Both players get the same eight pieces on the same eight files, so no arrangement hands White a resource Black does not have one move later. Engines have been pointed at the starting arrays, and the numbers they produce are small, sensitive to depth and settings, and disagree with each other. Quoting them here would be pretending to a precision that is not there.

So the word best on this page means interesting for a stated reason. Every grouping below was computed over all 960 arrangements with the same code that builds the position pages, and every number is a count you can check by opening the positions.

Which positions give White the most first moves?

Sixteen of them are always pawn moves, since the pawns start where they always start. The rest comes from the knights, because on move one nothing else can leave the back rank. A knight in the middle of the rank reaches two empty squares, a knight on a1 or h1 reaches one. That gives 18, 19 or 20.

The twenty-first move is castling. In 162 arrangements the king and its rook stand next to each other on c1 and d1, or on f1 and g1, which are the squares they castle to, so O-O is legal before anything else has moved. In 62 of those the knights are also both off the rim, and 21 legal first moves is the maximum any position offers. Position 81 and position 19 are two of the 62, and the castling page works through why a move like that is legal.

The full spread: 22 positions give 18 moves, 336 give 19, 540 give 20, and 62 give 21. Ordinary chess sits in the largest group.

At the bottom, 36 arrangements put both knights on a1 and h1. Fourteen of them get the move back as a castling move, which leaves exactly 22 positions at 18 first moves, the narrowest start in the game. Position 310 and position 366 are two of them.

21 first moves · BNNBRKRQ

18 first moves · NRKRQBBN

Position 81 on the left. The knights on b1 and c1 give four moves between them, and the king and rook on f1 and g1 give a fifth by swapping squares, so White has 21 first moves, the most any position offers. Position 366 on the right has both knights in the corners, one move each, and no castling, which is 18.

Which positions start with an undefended pawn?

In ordinary chess every pawn on the second rank has a defender except f2, which only the king guards. Shuffle the rank and that arrangement of cover changes completely.

In 600 of the 960 positions at least one second rank pawn is defended by nothing at all, and 144 have two. The corner pawns are the usual victims: a2 is undefended in 228 positions and h2 in 228, against 32 each for d2 and e2. The reason is plain enough once you see it. A rook on a1 covers a2, and a knight on a1 or b1 covers nothing behind it, so an arrangement that opens with two knights leaves both corner pawns bare, as in position 58.

SP 58 · NNRQBBKR

Position 58. The knights on a1 and b1 reach forward to c2 and d2 and cover nothing behind them, so the two highlighted pawns begin the game defended by nothing. This is the commonest shape of the undefended pawn: knights first, corner pawn bare.

The other 360 positions start with every pawn covered, though covered often means covered by the king, which is the weakest defender available and the reason f2 has a reputation. In 488 positions no pawn depends on the king at all. Take both tests together and 118 arrangements start with every second rank pawn defended by a piece, about one position in eight. Position 5 is one of them. That is the closest thing here to a computable claim of soundness, and it is still only a claim about move zero.

Where do the rooks start?

Both rooks stand in the corners in 108 positions, which is the standard chess arrangement and the one where castling does the most work, since it lifts a rook out of the corner and tucks the king away in a single move. Position 405 is one, and position 518 is the one you have played all your life.

At the other end, 348 positions have neither rook on a1 or h1. The rooks start closer to the middle, they see a file sooner, and the piece that needs rescuing is more often a bishop. The remaining 504 have one rook in a corner and one out. Which of the two a given position hands you decides most of the opening plan, which is the subject of the strategy page.

Where does the queen start?

The queen stands directly beside the king in 248 positions. It matters more than it sounds. Any line an opponent opens toward the king tends to arrive at the queen as well, and a check on the file or diagonal they share can pick up the queen behind it, which is the shape position 49 starts in.

SP 49 · BNNBRQKR

Position 49. Queen and king on f1 and g1, with a rook behind them on h1. Anything that opens the second rank or the long diagonal into g1 arrives at the queen on the way, and a check along the first rank hits both pieces at once.

Where do the bishops start?

Sixty positions put the bishops on b1 and g1, both fianchettoed before a move is played, needing only the pawn in front of each to step up. Another 60 put them on a1 and h1, as in position 3, and 420 positions put at least one bishop in a corner.

A corner bishop is the cheapest development in the game. Play the pawn on the b file or the g file one square and the bishop looks down the whole long diagonal, from a1 to g7 or from h1 to b7. That is one move for a piece that in ordinary chess needs a pawn move and a bishop move to reach the same square. If you are counting positions by how quickly you can get something aimed at the enemy king, these are the ones to look at, and the setup page shows the move on a board.

What is the best Chess960 position for White?

Whichever one you understand fastest. White's advantage is the same advantage as in chess, which is the move, and no arrangement adds to it, because Black's pieces sit on the same files.

If best means most familiar, the answer is position 518, the ordinary chess array and one of the 960. If best means most likely to produce a game you can steer, the 118 positions with every pawn defended by a piece are a defensible pick, and so are the 108 with both rooks in the corners, on the grounds that castling solves more of your problems at once. Neither claim is stronger than the reason attached to it, and that is the honest end of the subject. What the two games do and do not share is set out on the rules page.

How to use any of this

Open a number, look at the back rank, and play it. The generator page for each position lists its castling squares, its first move count and which pawns start weak, all computed rather than asserted. Take one that interests you, play it against the computer, and the properties stop being counts and start being the thing you are handling on move seven. For the tactics that come out of these arrangements there is the puzzle trainer, and a thousand of them per volume in the books.