Best move (3)

Position from Unzicker - Botvinnik (Oberhausen 1961). What is the best move for white?

Solution: 1.Re6+! forces mate in 7. The longest line is 1.- fxe6 (1.- Kxe6 2.Qc6+ Ke7 3.Qf6+ Ke8 4.Rb8+ Rd8 5.Rxd8#) 2.Qg7+ Kd8 3.Qxh8+ Kc7 4.Qb8+ Kc6 5.Rb6+ Kd5 6.Qa8+ Rb7 7.Qxb7#

Interestingly White did not see this blow. He played 1.e6 which is also winning but not that fast (though Black resigned on the spot).