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Endgame 7 (author Leo Spinger)
1a3c5The two square blocks allow a remarkable manoeuvre that's easy to remember ..., but first, let's consider a race between the white man on d2 and the black man on c6. It doesn't look promising to begin with, because white is a tempo down, but reality is even worse.

We'll take the symmetric 1. d2c3 for example, but d23 and d2e3 boil down to the same: 1.d2c3-c65!, 2.c3d4 (what else?)-a6c4!, 3.a4c6x-c4a2x, 4.c64x-a21 (a2b1 for those with an acute sense of irony)+
a5c3x
2c5a7xNow 2...c5b4?, 3.a7b8king+ and 2...c6d5, 3.a78king-d5e4, 4.a86-b65 (4...b6c5, 5.a6c8+), 5.b46x-c3b2, 6.a61-e4f3, 7.b67-g3g2, 8. b78king+
c3b2
3a78On 3...b2a1, 4.b4a5+ and on 3...b21, 4.a85+ while 3...b2c1 meets with 4.d2c3-c1a4x, 5.a83x+ and 3...c6b5 meets with 4.a82-b53x, 5.ac2x-b3a2, 6.c2b1! and white converts to a 2x1 king's ending.
c6d5
4a81d5e4
5b4a5e4f3The crucial position - now 6.d2c3?-f3g2, 7.ah1-b65! (7...b2a1??-h12!+ and 7...b6c5?-8.hb1!-b2a1king, 9.b15+) 8.ac5x-b2a1king, 9.c5b6-a17! (threatening a7b8), 10.c3b4-a7b8, 11.b45-b8a7, 12.b5c6-a76, 13.ha1-a68, 14.ah1-a86 ends in a draw by 3-fold!

White's only win is the gambit 6.d2e3!! which brings the black man to d3, depriving it from access to the corner!
6d2e3fd3x
7a56White is single minded here: he goes for b8 for an attack on the man on b2.
Black has two options: providing cover on b3 or sacrificing on the a-file (a sacrifice on the first rank never takes effect: 7...b6c5, 8.a6b7-d32, 9.b78king+).

Blocking on b3 offers more resistance: 7...b65, 8.a6b7-b54, 9.b78king-b43, 10.b8h2!-d3c2 (10...b3c2?, 11.ac1+), 11.h21 (11.ac1???-b3a2+)-b3a2, 12.a15x-b2a1, 13.a5e1+.

That leaves the sacrifice on the a-file.
b65
8a6b7b5a4
9a16xPreventing promotion in the corner.
b2c1king
10b78Black gets one fleeting moment allowing progress ...
d3e2
11a6111…e2d1K fails on 12.b81, and 11...c1f4 (to prevent white's access to h2) fails on 12.ae1+
ch1
12b81Black cannot promote and needs access to e3.
h13
13bh1he3
14a12e3d2
15h12Tableau!