[Retros] Double-pin mate

[Nicolas.Dupont at math.univ-lille1.fr]

Andrey asked :


> How many pins can be effective in the mate position of an SPG (regardless

> of the mating piece)? Three? Four? Or even more?


It's not so complicated to get four...

1.Pa2-a4   Ph7-h5   2.Pa4-a5   Ph5-h4   3.Pa5-a6   Ph4-h3
4.Pa6xb7   Ph3xg2   5.Ph2-h4   Pa7-a5   6.Ph4-h5   Pa5-a4
7.Ph5-h6   Pa4-a3   8.Ph6-h7   Pa3-a2   9.Th1-h6   Pa2xb1=T
10.Cg1-h3   Pg2-g1=T 11.Ta1-a3   Tg1-g5   12.Ta3-g3   Ta8-a1
13.Ph7xg8=T Cb8-a6   14.Pb7-b8=T Fc8-b7   15.Tb8-c8   Fb7-h1
16.Pe2-e4   Pc7-c5   17.Ff1-b5   Pc5-c4   18.Dd1-h5   Tg5-c5
19.Pf2-f3   Pe7-e5   20.Th6-e6

Obtaining five effective pins needs of course a completely different kind
of strategy (the thematic king must probably stand around the center of
the board). It should probably exists, although I have strictly no idea of
how getting it.

Other researches can be made on that 4-pins task. For examples :
- fewer moves
- no visible promoted piece
- AUW-like