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With 4...Nxe4 Black takes the pawn and hopes to survive the white attack. White should take on d4 with 5.Qxd4 (see diagram on the left) because if 5.0-0?!, hoping to head into the anti-Lange lines of the Two Knights Defence following 5...Nc6?! 6.Re1 d5 7.Bxd5 etc., Black can cut out the Bxd5 tactic by playing 5...d5! immediately.
Here Black normally retreats the knight to f6. The tempting 5...Nd6?! is met by 6.0-0, intending to bring the king's rook to e1 with check. Black then cannot grab the bishop-pair with 6...Nxc4? because Black then cannot parry the check on the e-file without leaving g7 unguarded: 7.Re1+ Be7 8.Qxg7 Rf8 9.Bh6 wins for White. |
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Following the normal 4...Nxe4 5.Qxd4 Nf6, White should play 6.Nc3, adding much-needed protection to the d5-square. If instead 6.Bg5?!, Black continues with 6...Nc6 intending 7...d5; see Grabliauskas-Gysi, email 2002. Michael Goeller may have been the first to point this out at his Urusov Gambit site back in 2002. In Danish Dynamite Muller and Voigt say that "White has to pull out all the stops to keep the balance", but I am not convinced that White can even achieve that.
After the superior 6.Nc3, Black can then try to hit out in the centre with 6...Be7 7.Bg5 c6 8.0-0-0 d5 (see diagram), and if White had to immediately retreat the bishop on c4 here, Black would be doing rather well. However, White can maintain the bishop on c4 for a few more moves by playing 9.Rhe1 (pinning the bishop on e7, so that if 9...dxc4? 10.Qxd8#), or 9.Qh4, pinning the d5-pawn. These two moves tend to transpose to each other. After 9.Rhe1 the main continuation is 9...Be6 10.Qh4 Nbd7, and then either 11.Bd3 or 11.Ne4!?, with considerable complications in which White has reasonable compensation, see Zavanelli-Pope, corr. 1987. |
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Instead following 4...Nxe4 5.Qxd4 Nf6 6.Nc3, Black can hit out at the white queen with 6...Nc6 7.Qh4. Then 7...Be7 usually follows, adding protection to the knight on f6, and then 8.Bg5 (see diagram).
Black should be wary of castling early; for a scary example of 8...0-0 see Taylor-MacGregor, email 2012. Instead 8...d5 doesn't work so well because of 9.0-0-0 and then if 9...Be6 10.Nxd5!, see Amann-Contreras Poblete, email 2006. So Black normally plays 8...d6 9.0-0-0 Be6. Then 10.Bd3 is dubious because of 10...Ng4 (Goeller), so White chooses between 10.Bxe6 fxe6 11.Rhe1 (although this gives Black a good way to return the pawn and reach equality) and the more challenging 10.Rhe1 Bxc4 11.Qxc4 0-0. Black has been able to disrupt White's attacking setup and push the queen away from the kingside, and then get castled. Despite this, the line isn't a serious threat to the viability of White's gambit, and White has a few good ways to continue the attack. 12.h4 is probably the most promising try, see Burkett-Spiridonov, email 2003. |
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This defence has generally been underestimated for Black. Following 4...Nxe4 5.Qxd4 Nf6 6.Nc3 Nc6 7.Qh4 Bb4, Black aims to play ...Bxc3(+), exchanging off the knight on c3 and, most importantly, shattering White's queenside pawn structure. This means that White cannot safely castle queenside, and kingside castling has its downsides: White has to spend an extra move getting the two rooks to the central files, and White is also less well-placed to attack down the h-file and/or launch a kingside pawn storm if Black castles kingside. A key idea for Black is to try to favourably provoke the Bxh6 sacrifice.
White can try to continue as normal with 8.Bg5 Bxc3+ 9.bxc3 0-0 10.0-0-0!? h6 11.Bxh6 gxh6 12.Qxh6 d5, but due to the exposed white king on the queenside, Black can force a quick draw. Thus White usually continues 8.0-0 Bxc3+ 9.bxc3 0-0 10.Bg5, but then Black continues 10...h6! 11.Bxh6 gxh6 12.Qxh6 d5, see Grobler-Antal, email 2011, and it is not clear if White has enough for the piece. |