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

232 OPEN SLAV DEFENCE
lcgally possible. Wlire has a choicc of 20 Iirsr
movcsi Blact the saoe number ofreplies, making
400 differenl possiblc positions after one move
each. In 1895 C. Flye St Marie calcllaled that
7 I .852 difie rent legal posiiions we.e possi bl e atter
two mo,es bv each pl.yer. This fie!.e is geometrically
onect but in 1946 DAwsoN shosed that
Wbile might have thc option oI an N p ssANr
capture in 232 of these positions. depending on
$hich ol about 200,000 differeni playing sequences
were chosen. Frc6 a chess poinr oI view, therefore.
?2,084 dificrent posirions are possible.
Aiter three noves each morc than 9,000,000
positionsarePossible. To arnve at every onc ofth.
possible positions alter four moves each at the rate
otone position aminul€ day and nightwolld take a
player 600,000 years. Tbere a.e 2xlor possible
difterent legal positions on a chessboard. and ii
bas been estimated that the nunber of distinct
40 nove games is 25x10'8, far grealer than the
eslimated number ol eledrons in ihc univeBe
(10i). (For anolher asrronomical nsurc sec
OPEN SLAV DEFENCE, 38. IhE
'2!'! DEITNCE,
OPEN TOURNAMDNTT a iournament tnat- nomi
nallyatleasl, nas no reslriclion on entry. Tbns thc
open chatuPionsbip ofa counlry nay be won by a
non-rcsident.ln pradice entry to a! open rourna
nent may dcpend on. ninimtrn levcl ofprolen
OPPONENT, specidelly one who does not have
the oove; generaly tbe adversary of atr idetriified
OPmSITE COLOIIRED BISEOPS. see nrsH6pq
OPPOSITION. a speci l relaiionship betwcen lhe
positions ol thc kings pardy depe.ding on the
distaDce belween them. rhe unil ol neasurenent
is the dntance belween the centrcs of 1wo laterally
adjoining squares. The kings stand in opposition
when a) thc posilion is a zuczwANc and b) the
co-ordinales of the distan.c betNeen the kings
co.sisl of even nunbers as folloss: 2.0, dnect
oprositionj 4,0, distant opposition: 6,0, lons'
disranr opposirioni2.2. (v8) or 4,1, (v32) or6,6,
(vr2), diaso.al oppositioni 2.4. (v20) or 2,6.
(V4l) or a,6, (V52), oblique opposition. Tbe
opposition may also be caled vertical lor kin8s
standing on thc same nle, horizonlal for kin8s
sranding on the samc rank. (Zugzwang is an ee
s€nlialconsdtuenti yeirhetcrm opposiiion isofien
misusedtodescribeanysnuiiioninwhicbthekings
stand as close as possible on lhe sane r.nk or file.)
When lhe kings siand in opposition theplayerNho
does nolhave rhe nove is said looselyto have the
oppositioni ilhecreatessucb apositionheissaidto
take the oppositioni iI he dravs the gane by
maintaining the opposition hc is said 10 hale the
oPoaENSKi, Karet (1892 197s), Czech player,
lnternational Master (1950), International Arbito
(1951), nalional champion 1929 and 1944. cochampion
1927. 1938, and 19,13, civil seBanl. A
nemberofthe Czech team in lour or.yMqADs from
19311o 1939. he nade the best fourth-board score
(+10=3) at Foltcsrone in 1933. His b€st rournamcnt
achievemenr sas atBadsruben (stubnansk€
Teplicc) 1930, sben he shared third prne wilh
ELoHR and dr.c after LTLTENTSAL and prRc.In later
life he took an adivc paft in cbeas organization.
sening on several .rDr committees, and he was
chiefa.bircr for the world championship natches
OPOaENSXi (iAMBIT, i32, ALEorN.\ name
tor the BEN(o cAMBrr. beslowed alter oroaENsd
had played it against rri.rurRG, Podebrady 1936.
OPOaENSKi OPENiNG, 224, also known as rhe
Tro6possly Ope.ing, played by JANows{ in the
1920s, hy orcaENsKt in the l93os, and by his
countryman troRr in the 1970s.
OT,O.ENSKI VARIATION, ]81in the GR,NFELD
D.mNcE as in the game Opoicnski-Pachman,
P.ague 1947i264in the srduN D!lrN.E, an idca
The kings sland in verti.al direct opposition.
White to play draps: I Ke5 KeTz (z synboDes
zugzwang) 2 Kd5 Kd?z 3k5Kcrz 4b5(Unablc
to advane bis king White advances bis payn
instead.)4. . . Kb7 5b6rb8 6Kc6Kcaz 7b7+
(b82. Blackioplayloses: I ,Ke7 2(e5zKd? 3
KdszKcT 4Kc5zKb7 5 (bszKa? 6Kc6(White
mates ad outflanking mancuvre. ) 6 . . . Kb8 7 b5
(a7 8 Kc7 Ka8 9 (66Kb8 10 Ka6 Ka8 1l b6z
Kbs 12b7z.It isa. i. h erenl cha.acte sticofthis
pa*n lomation (a single white pa*n al b4) that sir
zuEzwangs are possible: theseoccurwirh the whire
king on a5. b5. d, d5. e5, or f5 and the blackldng
on a7 . b7 , cl , d1 , e7. o. l, respedivelr. These
reladonships may be shoNn thus a5=a?, b5=b7,
and so on, each equarion representing a pan oi
sqDares known as .oNruGAE souaREs, a term