Correct answer: Nc2-a1 1.Nc2-a1 ! zugzwang. 1...Nb5-d4 2.c3*d4 # 1...Nb5*a3 2.d3-d4 # 1...Nb5*c3 2.d3-d4 # 1...Nb5-d6 2.d3-d4 #