[Retros] Original by Kari Karhunen

[Francois Labelle]

Solution:

White is afraid of
1. ?? Na6 2. a4 Nb4 3. d4 c6 4. Ra3 Qa5 5. Rd3 Nxd3#

The only moves that avoid this are:
1. Nc3
1. c3
1. e3
1. e4

Three of these moves can still lead to 5... NxR#:
1. Nc3 Nf6 2. Nd5 Ne4 3. Nxe7 Nxf2 4. Nc6 Qh4 5. g4 Nxh1#
1. c3 Nc6 2. h4 Nd4 3. Rh3 Nxe2 4. Rd3 Nxc1 5. Ne2 Nxd3#
1. e4 Nf6 2. Qe2 Nxe4 3. f3 Ng3 4. Qxe7+ Qxe7+ 5. Kf2 Nxh1#

So by elimination the first move must be
1. e3

My computer confirms that 1. e3 ... 5... NxR# is impossible, so the 
problem is C+. Nice problem!

     François


On 09/18/2013 09:12 AM, Olli Heimo wrote:

> Hi! I showed some our discussions to Kari Karhunen. He is IM in solving and he suggests the following problem claiming that it is sound. I have not yet solved it. Olli. Solutions please.

>

> Kari Karhunen, original for retro mailing list.

> White wants to avoid any possibility that the game ends with 5. - NxR#.

> Which was the first move by White.

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