[Retros] Add pieces

[Theodore Hwa]

On Sat, 12 Mar 2011, Noam Elkies wrote:


> Theodore Hwa <hwatheod at cs.stanford.edu> writes:

>

>>> it would be difficult to compose a problem in which it is not

>>> possible to add an additional piece (although not impossible).

>

>> Here's one possibility with 30 units, nobody in check:

>> Starting from the initial position, remove the queens,

>> and move the kings over to the queens' original squares.

>> It is not possible to add any pieces.

>

> Neat.  Possibly reducible to 28: move each King one square further,

> removing the Bc1 and Bc8.  Or even 26, going back to T.Hwa's position

> but putting a2,h2,a7,h7 on b3,g3,b6,g6 and removing all four Knights

> (or some suitable combination of Knights and Rooks).  26 could then

> also be attained by a mixture of the two techniques: put the Kings

> back on c1 and c8, and play only h2xg3 and h7xg6; or put just wK on c1

> and add a7xb6.


Extend this technique to achieve 22:

Remove all queens, knights, rooks.  Move kings to d1/d8.  Move a2,a7,h2,h7 
to c4,f4,c5,f5.

Ted