1...e5  2.g8=Q#

1...Qb1  2.Rxd4#

1...Rxf4  2.Sxf4#

1...Rxc4! a

1...Qxc4! b

1.Qa8?  [Rxc7#]

1...Rxc4 a  2.Rc5# A

1...Qxc4!

1.dxc7?  [2.Sxb6#]

1...Rxc4 a  2.Rd6# B

1...Qb1  2.Rxd4#

1...Rxf4  2.Sxf4#

1...Qxc4! b

1.Qb1?  [2.Qb5#]

1...Qxb1  2.Rxd4#

1...Rxc4! a

1.Qa2!  [2.Sxb6#]

1...Rxc4 a  2.Qxc4# C

1...Rxf4  2.Sxf4# 

- Interchange of functions between two units: A and B after the same defence. In a try the piece A pins and piece B mats. In actual play piece B pins and piece A mats.

(*The checkmate is possible because bRd4 is pinned by the Rook

**The checkmate is possible because bQc4 is pinned by the Queen)

See in next article in "Problemas", magazine of October 2020, with more examples.

- Kharkov 1

- Double Kharkov 2