Parhamov vs Jacoobsen: game review

37.Rxa6 is a mistake: White's winning chances go from 44% to 32%.

• Black answers 37…Re2: the rook reaches the seventh rank, where 3 pawns sit.
• After Re2, Black wins 2 points of material within 6 moves.
• Better was 37.Rc4 (−0.66), which attacks the c7 pawn, which is undefended.

Better: 37.Rc4 attacks the c7 pawn, which is undefended, and shores up the c2 pawn. Engine line: 37…Re2 38.Qf1 Nf6 39.Rd1 d5 40.Rc3 (−0.66).

37…Re2! The only good move here: every alternative is clearly worse.

• The rook reaches the seventh rank, where 3 pawns sit.
• Adds a decisive attacker on the g2 pawn: 2 attackers against 1 defender.
• The next best move, 37…Nb6, would drop Black's winning chances from 68% to 54% (−0.40).
• 37…Re2 wins two pawns, picking it up with 38…Rxc2.
• Sets up a sequence and wins two pawns once the captures settle, picking it up with 38…Rxc2.
• White answers 38.Qg1.

39…Qe4 lets the win slip: 39…Qxb2 kept Black winning. Black's winning chances go from 79% to 61%.

• White answers 40.Bg3: moving away uncovers the queen on f1, which now hits the f7 pawn.
• Better was 39…Qxb2 (−3.65), which takes the pawn on b2.

Better: 39…Qxb2 wins two pawns and trades off the attacked queen instead of losing it to Rxc2. After 40.Bg3 Rxg2+ 41.Qxg2 Qxc1 42.Rc6 Qe3 43.Rxc7 Ne5, Black comes out a pawn up (−3.65).

40…Rxg2+!! A real sacrifice: Black gives up material and the engine still rates it best.

• Puts the rook on g2 where it can be taken.
• White can take, but after 41.Qxg2 Qxf4+ 42.Kh1 Re1+ Black mates in 6.
• Takes the pawn on g2.
• The rook forks the king and the pawn: both can't be saved at once.
• 40…Rxg2+ forks the king and the pawn.
• The rook joins the attack: it now hits 3 squares around the White king.

• The idea: 40…Rxg2+!! offers the rook on g2. Taking it leads to mate.
• What Black gives up: 40…Rxg2+ puts the rook on g2 where it can be taken by the queen on f1. That's a whole rook on offer.
• If White takes the rook: 41.Qxg2 is met by 41…Qxf4+, taking the bishop on f4 with check. Then 42…Re1+ gives check, and 43…Qf3+ gives check. Black forces mate in 6. This is White's best try.
• Without the sacrifice: The best move without the sacrifice, 40…Ne5, is clearly weaker (−0.68 against #−6). White answers 41.Ra3, preparing Qf2 and Qc2. That would leave Black a little better.

• Both sides followed opening theory up to 8…Na5: 16 moves in all, 8 by White and 8 by Black.
• Theory runs out after 8…Na5: too few games between strong players reached this position to go further.