1.Ne4!	Nd3
After 1....g1=Q+ 2.Nf2+ the new Black queen is lost
2.Qf2!!	Nxf2
Again 1....g1=Q+ 2.Ng3+ loses the new Black queen
3.Ng3+	Kg1
4.Ng5
Zugzwang. After any Black knight move, he is mated.
Guvrich (1927)