This move is not just threatening a rook, but also enabling the tactical idea of e6 and Qf6.

By now the powerful dark square blockade and the exposed black king outweigh the pawn.

By advancing the e-pawn before it is blocked by Nc3-e4, Black frees the a1-h8 diagonal and the e-file for an attack on the white king.

2.Bxe4? Re8 -+
2.Qxe4 Qf6! 3.Nd1 f3 , followed by 4...Qa1, Black obtains a strong initiative – Tal.

3.Kh2 Qh6+ 4.Bh3 f3! 5.Qf1 Qh7 with strong pressure.

In the same spirit as two moves ago, before White arranges a blockade by Bg2-f3.

Thanks to the double threat at f3 and g1, Black wins material.

Tal later converted his extra exchange into victory.

Finishing off Black's idea of ...Nd7-c5 with a blockade.