B51 Sicilian Defense: Moscow Variation
B51 holds three named lines, all under the name Sicilian Defense. It leaves B50 (Sicilian Defense: Modern Variations) with 3.Bb5+. Black, to move in that position, has four legal moves, the fewest of all 500 codes. The reference line ends with a check, 3.Bb5+. Only six of the 500 reference lines end this way.
| # | White | Black |
|---|---|---|
| 1 | e4 | c5 |
| 2 | Nf3 | d6 |
| 3 | Bb5+ |
The move that completes B51
The reference line of B52 plays all of these moves and continues beyond them; B51 is the position reached at 3.Bb5+.
- 3.Bb5+ The bishop leaves f1 for b5, opening a line for the rook on h1, giving check.
Lines filed under B51
All three share their first five plies, the whole reference line.
| Name | After the shared start | Plies | At the end |
|---|---|---|---|
| Sicilian Defense: Moscow Variation | (the shared start itself) | 5 | check |
| Sicilian Defense: Moscow Variation, Dorfman Gambit | 3...Nc6 4.O-O Bd7 5.Qe2 g6 6.e5 | 11 | White castled |
| Sicilian Defense: Moscow Variation, Moscow Gambit | 3...Nc6 4.O-O Bd7 5.c3 Nf6 6.Re1 a6 7.Bxc6 Bxc6 8.d4 Bxe4 9.Bg5 | 17 | Black +1, White castled |
Sicilian Defense: Moscow Variation, Dorfman Gambit
- 3...Nc6 The knight leaves b8 for c6, opening a line for the rook on a8.
- 4.O-O White castles kingside, opening a line for the queen on d1, guarding the pawn on g2.
- 4...Bd7 The bishop leaves c8 for d7, opening a line for the rook on a8 and the queen on d8.
- 5.Qe2 The queen goes from d1 to e2, opening a line for the rook on f1, guarding the pawn on e4 and the bishop on b5.
- 5...g6 The g-pawn advances to g6, covering f5 and h5, opening a line for the bishop on f8.
Sicilian Defense: Moscow Variation, Moscow Gambit
- 3...Nc6 The knight leaves b8 for c6, opening a line for the rook on a8.
- 4.O-O White castles kingside, opening a line for the queen on d1, guarding the pawn on g2.
- 4...Bd7 The bishop leaves c8 for d7, opening a line for the rook on a8 and the queen on d8.
- 5.c3 The c-pawn advances to c3, covering b4 and d4, opening a line for the queen on d1.
- 5...Nf6 The knight leaves g8 for f6, opening a line for the rook on h8.
The road to B51
- 1.e4 … 1...c5two earlier stops: B00, B20
- 2.Nf3B27 Sicilian Defense
- 2...d6B50 Modern Variations
- 3.Bb5+B51
The position after 3.Bb5+
White has brought out the knight on f3 and bishop on b5; Black has not yet moved a knight or bishop.
Codes that branch off from B51
The reference lines of one other code leave B51 from the position after 3.Bb5+, each with its own moves.
| Code | Moves | Reference line |
|---|---|---|
| B52 | 3...Bd7 | Sicilian Defense: Moscow Variation, Main Line |
Closest boards in other codes
| Code | Line | Differs on |
|---|---|---|
| B27 | Sicilian Defense | four squares: f1, b5, d6, d7 |
| B20 | Sicilian Defense | six squares: f1, g1, f3, b5, d6, d7 |
| B28 | Sicilian Defense: O’Kelly Variation | six squares: f1, b5, a6, d6, a7, d7 |
| B29 | Sicilian Defense: Nimzowitsch Variation | six squares: f1, b5, d6, f6, d7, g8 |
| B30 | Sicilian Defense: Old Sicilian | six squares: f1, b5, c6, d6, d7, b8 |
| B31 | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack, Fianchetto Variation | six squares: c6, d6, g6, d7, g7, b8 |
| B40 | Sicilian Defense: French Variation | six squares: f1, b5, d6, e6, d7, e7 |
Where lines continue from here
Three named lines filed under other codes pass through the position after 3.Bb5+. All of them belong to the codes listed above.