Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Nf6/4. Ng5/4...d5/5. exd5/5...b5

Ulvestad variation C57 Two knights defence → 4. Ng5 → 5. exd5 5...b5 · Ulvestad variation Black offers a pawn to deflect the bishop from control of d5 and pressure of f7, so that they may retake on d4 with the queen. If White accepts the sacrifice, 6. Bxb5?!, this works out well for Black. 6...Qxd5 and both White's bishop and the g2-pawn are under attack. If White trades, 6. dxc6?! bxc4, Black has equalised. 6. Bf1! is the surprising refutation. Un-developing the bishop guards g2, and though Black may retake the pawn with their queen, they'd be hit by Nc3 with tempo (6...Qxd5 7. Nc3), so the main line involves 6...Nd4 as in the Fritz variation. History The move was suggested by Olaf Ulvestad in Chess Review in 1941, where he expressed dissatisfaction with the main move, 5...Na5:A New Move in an Old Defense Chess Review Ulvestad Olaf I. 1941 January 7-8 is it absolutely necessary to move the Knight [to a5]? ... Black must lose time getting it back into the game [and] it is in no way a real counter-attack, as it permits the very strong reply [Bb5+]. From these considerations, it became more and more obvious to me that [5...Na5] is a weak, ineffectual move which actually violates the principles of good chess... In positions like this, one should look for possible counter attacks. After 5...b5, Ulvestad analysed 6. Bxb5, 6. Bb3, 6. dxc6, 6. Bf1 and 6. Be2 and judged that White could not hold an advantage. To 6. Bf1, considered the best move today, he suggested 6...h6 and analysed 7. Nf3 and 7. dxc6, but did not appreciate that White was better after 7. Nxf7 Kxf7 8. dxc6. Theory table 1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 d5 5.exd5 b5 Ulvestad Variation 6 7 8 9 10 Bf1Nd4 c3Nxd5 Ne4Qh4 Ng3Bg4 f3e4 ∞ Bxb5Qxd5 Nc3Qxg2 Qf3Qxf3 Nxf3Bd7 O-OBd6 = dxc6bxc4 Qe2Qd5 f4Qxc6 fxe5Bg4 Nf3O-O-O = References See also Two Knights Defence