Starting position #423
Back-rank setup: RNBQNKRB
SP-423 · BastionGuard — King shifted to c or f, knights kept clear of the edges — 168 positions in all.
Move the pieces right on the board — full Chess960 rules, castle by dropping the king on the rook.
Position features
The king starts on f1, the rooks on a1 and g1, the queen on d1.
Castling short simply swaps the two pieces: the king on f1 and the rook on g1 trade places.
A bishop starts in the corner on h1: it has a single diagonal, which the g-pawn unlocks, running out to a8.
One second-rank pawn starts with no defender at all: h2.
The setup belongs to the BastionGuard family; read right to left it becomes position 722.
The engine's main line opens with d4, putting a pawn straight into the centre.
Every sentence here is computed from the setup itself and can be checked on the board.
Balance
MBI 86 Morozov Balance Index: 86 of 100 — class A — most balanced.
- Engine evaluation of the starting position: +15 centipawns for White (depth 46, 400 000 000 nodes).
- Rank 136 of 960 by balance — 1 is the most balanced start.
- Balance band S — slight edge · dynamics along the play-out: stable
- Evaluation along the engine's main line (70 half-moves): +30 → +17 → +10 → -7 → 0
- Deeper check (1 200 000 000 nodes, depth 51): +11 cp, -4 cp against the base run — verified
Position facts
- Mirror twin: position #722
- The king starts on f, the rooks on a and g
- King and rook are neighbours — castling from adjacent squares feels unusual
- This position does not come up as the daily position in the next four years
Puzzles from this position
- Winning blow: queen to e5 — Chess960 specifics · 780
- Attack on the uncastled king: pawn to h3 (g2·7) — Chess960 specifics · 780
- Attack on the uncastled king: rook to g4 (g1) — Chess960 specifics · 780
- Attack on the uncastled king: knight to c3 (b1·2) — Chess960 specifics · 780
- Attack on the uncastled king: queen to d4 (d1·7) — Chess960 specifics · 780
- Attack on the uncastled king: knight to f3 (e1) — Chess960 specifics · 970
- Winning blow: knight to d6 (b5·14) — Chess960 specifics · 1280
- Mate in 3: knight to d7 — Chess960 specifics · 1630
- Mate in 3: rook to e7 (e1·7) — Chess960 specifics · 1860
- Attack on the uncastled king: queen to d8 (d3·3) — Chess960 specifics · 2350
This position appears in course day 35
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Commentary
Short castling swaps the king on f1 with the rook on g1. A bishop holds the corner on h1 with one diagonal to a8; the second bishop is on c1. On the second rank, h2 has no defender, and f2 leans on the king alone. The queen is on d1, the knights on b1 and e1, the second rook in the corner on a1. The engine takes the centre with d4 and the line runs d4 d5 c3 Nd6 Nd3 Nd7.
Written from the measured facts above and checked against the board before publishing. All 960 positions have one.