Starting position #739
Back-rank setup: BRKNNQRB
SP-739 · BastionGuard — The king starts one file off-centre, on c or f, with neither knight in a corner.
Move the pieces right on the board — full Chess960 rules, castle by dropping the king on the rook.
Position features
The king starts on c1, the rooks on b1 and g1, the queen on f1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
A bishop starts in the corner on a1: it has a single diagonal, which the b-pawn unlocks, running out to h8.
The second rank carries 2 pawns with no defender at all: a2, h2.
The setup belongs to the BastionGuard family; read right to left it becomes position 403.
The engine's main line opens with b4.
Every sentence here is computed from the setup itself and can be checked on the board.
Balance
MBI 99 Morozov Balance Index: 99 of 100 — class A — most balanced.
- Engine evaluation of the starting position: +4 centipawns for White (depth 47, 400 000 000 nodes).
- Rank 8 of 960 by balance — 1 is the most balanced start.
- Balance band E — even · dynamics along the play-out: stable
- Evaluation along the engine's main line (53 half-moves): +28 → +21 → 0
- Deeper check (1 200 000 000 nodes, depth 49): +9 cp, +5 cp against the base run — verified
Position facts
- Mirror twin: position #403
- The king starts on c, the rooks on b and g
- King and rook are neighbours — castling from adjacent squares feels unusual
- It becomes the daily position in 1006 days
Puzzles from this position
- Attack on the uncastled king: pawn to b3 (a2·20) — Chess960 specifics · 780
- Winning blow: knight to e7 (d5·8) — Chess960 specifics · 920
- Attack on the uncastled king: king to d1 (c1·3) — Chess960 specifics · 970
- Attack on the uncastled king: queen to d7 (d3·5) — Chess960 specifics · 1010
- Winning blow: rook to f7 (f6) — Chess960 specifics · 1200
- Attack on the uncastled king: queen to d5 (d4) — Chess960 specifics · 1250
- Mate in 3: knight to b6 — Chess960 specifics · 1630
- Attack on the uncastled king: queen to c6 (e4·2) — Chess960 specifics · 1630
- Mate in 3: rook to g8 (g2) — Chess960 specifics · 1630
- Attack on the uncastled king: rook to c5 (c1·12) — Chess960 specifics · 1860
This position appears in course day 22
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Commentary
The engine finds almost nothing for White here: +4 centipawns at depth 47. Both corners hold a bishop, a1 towards h8 and h1 towards a8, each with a single diagonal — and in the line the second one is traded off in place: after b4 b6 g3 comes Bxh1, and White takes back in the corner: Rxh1 f5. The king already stands on c1, so long castling moves the rook alone from b1. Two pawns begin with no defender at all: a2 and h2, and d2 leans on the king alone. The queen is on f1, the knights side by side on d1 and e1.
Written from the measured facts above and checked against the board before publishing. All 960 positions have one.