[Retros] Add pieces

Theodore Hwa hwatheod at cs.stanford.edu
Sat Mar 12 01:40:19 EST 2011

On Fri, 11 Mar 2011, Theodore Hwa wrote:



> 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.

Does this work? (18 units)

Put all white pawns on 5th rank.
Put all black pawns on 4th rank.
Kings anywhere not in check.


More information about the Retros mailing list