In each phase, only two pieces play, one white and one black.
Two forms of the theme can be distinguished:
Mixed forms are also possible. At least two phases and two moves are required. This is the theme of the 7th Azemmour TT (Vilnius, 2019). In Helpmate Analyzer, helpmates in two moves require at least three phases for the theme.
Sonnenfeld, Felix Alexander
Schach-Echo, 1976
1.Rxg3
Rb1
2.Rxg5
Rf1#
1.Bxd2
Bf1
2.Bxg5
Bh3#
1.h6
d3
2.hxg5
dxe4#
1.Se6
Sg6
2.Sxg5
Sh4#
Onkoud, Abdelaziz
M. Gafarov-80 MT, 2016
2nd Prize
1...Rb4
2.Rh1
Rxb6
3.Rh7
Rb8#
1...Rc4
2.Bc2
Rxc6
3.Bh7
Rc8#
1...Rd4
2.Qd3
Rxd6
3.Qh7
Rd8#
1...Re4
2.Rh3
Rxe6
3.Rh7
Re8#
Csák, János
idee & form, 1991
4th HM
1.Bb3
Sb2
2.Bc2+
Sd3
3.Bd1
Sf4#
1.Rh1
Se3
2.Rhg1+
Sg2
3.Rgf1
Sf4#
1.Kd3
Sb6
2.Ke3
Sd5+
3.Ke2
Sf4#
Pachl, Franz
Barth, Michael
Azemmour TT-7, Vilnius, 2019
1st Prize
1.d5
Rh7
2.dxe4
Rd7#
1.d6
Bf4
2.dxe5
Be3#
1.dxe6
Se3
2.exf5
Sxf5#
1.dxc6
Sc3
2.c5
Sb5#