chess-The Oxford Companion to Chess - First Edition by David Hooper & Kenneth Whyld

38 BLOC(
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A problem by vu(c[vrcn thatwon 6rsl prize in the
Feenstra-Kuiper Mcmorial tourney 1971. Tbe
posirioD n a block with tbree sel play nares:
1...Nf- 2Q93,1...Nxb5+ 2 Raxb5. and
1 . . . Nd- 2 Oxe4. Thcrc is a DUAL aie. I .
Nf5 (2 Qxc,l, 2 Nxc6). Having the nove, white
cannot maintain rhis bloct,lor be has no wailing
mole. Thekey,1Qa1, tbreatens nothinC. but scts
1 . . . NI5 2 NxE6 (the dual vanishes)
1 ... Nd- 2 Kc4. or 1 . .. Nl- 2 Kd2
I Bf5 ,Nl.1.rl R- 2(d3orKaB
The key changes one block lor another, and this
kind of problem is.allcd a mulatc.'thc idca sas
invented by SH'""$AN in 1877 and named by tbe
Enelish composer Bnan Harley (188!1955) id
1919 (For anolher example see csANcED MAm.)
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A p.oblem bysroccsithatNonsecondpize in the
Probleemblad rotncy 1951.I he position is a block
{ilhsetplayloreverybla.kmovc.c.g.l e5 2
N15,1. . . c5 2 Nb5.1. .Rd7 2Nxc6,1...
Bs2(hl) 2 Nxe2 Tlekeyis 1Bxd5 (threateni.s2
Qac4) and lour variations sh
... Bad5 2 Nxe2.
This kind of problem is called a block-thrcal.
The position is a btock, but White can neither
nainrainthh blo.k (as in awaired norsetup a new
block (as in a nurare). and rhe kc_\, nakes a $rear.
Foranother example see the problem ei,cn under
A probleh by BwE, llogfor Sakkald. 1913.
Although there are somc sct play mates (e.s.
1...93 2 hxg3) there are none after 1 .Be3-1
.. Rf5. l...Rg5.andl...d4,andtheposition
isnotablock:burtheke!,1Nxe5, sek un a blockl
1...8e3 2Ne2.1. . . R15 2Nd3.l. . . Rg5 2
Ng6.l. . . d4 2Oxd,l.1 Rh4 2QI8.TberRY,
1 Rf,e5. is deleared only by 1 . . . Rg5
This kind ot problem, id wbich rhe key com
pleres. parlly buill hlock. is called.n incomplctc
b10.k problcm. (For other examples see conurNrD
PrPEs, {nd RUGL6 rtsFME )
BLOC(ADE, a pawn formalion that .anno1,
wirhour sacrilice. be asailed by lrontal atta.ki a
pawn blocted by a piece, oi trvo or more such
paxnsi any situltio. in Nhich a player sers up a
delensive positionNhich is hardtobreak. Cederal
ly. blockades concern rhe.entralpart ofthc board
and many oi tben tak€ rhe lornr of locked
,AwN-cnarNs. A plaver nomallv .nacks tbe'base'
ofihe€nemychah.c.g. aller 1e4e6 2d,ld5 3e5
Black plats 3 . . . c5 Somctim.s a player tiies lo
prelenr !n aftack on bis cbain (pRopHyrAls)l
sonctimcs thc chain 6a! be broken by sacrilice.
bul more olten ptavcrc rcsort lo oulflanking
naneuues. These p.ocedurcs. laid down by
ptrrltDon, we.e brillianlll exemplilied by NrMzowrrs.r,
in his books. For soBe blockades that are
oudanked on thc qucc.\ side see loarNNr( ud
zuERroRr. Ior a ki.gi sidc ontflanking sec
AvrRu{(H, R. E. BYRNE, and.ErcoRrN. For a
blockadc maintained by two Lnights see the game
won b_v prrxosy^N uDdcr pAs\ FoRMArroN
Ninrzositzsch, a/a.[dde (1980) is ad English
ir&sladon oI a bookler and three ariiclcs on rh.
Pilhhury L.skc Nurcnbcry 1896
h thn sR'LUA\.y pR,zE ginc whnc bicaks thtuugh by
sadin.c 1c4e6 2d4di lNclNl6 4e5Nrd7 514.5 6
NB Nc5 l2 Be:r NhdT 1:r 0 0 p6 (piophyhxis. bul nor