Editing Threefold repetition (section)

===Portisch vs. Korchnoi, 1970===
{{Chess diagram
|tright
|Portisch vs. Korchnoi, 1970

|  |  |bd|  |nd|rd|kd|  
|pd|  |  |pd|  |nd|pd|pd
|  |  |  |  |pd|  |  |  
|  |qd|nl|  |  |  |  |  
|  |  |  |  |  |pl|  |  
|pl|  |  |  |  |  |pl|  
|  |pl|  |  |  |ql|bl|pl
|rl|  |  |  |kl|  |  |rl
|Position after 21...Qb5 with Portisch in a better position
}}
A famous draw for threefold repetition occurred in the fourth{{refn|"Lajos Portisch comments on the controversy surrounding his draw against Viktor Kortschnoi in their fourth and last game." per ChessBase article<ref name="ChessBasePortisch" />}} game<ref>{{cite web|url=https://www.chessgames.com/perl/chessgame?gid=1081983|title=Lajos Portisch vs. Viktor Korchnoi (1970)|publisher=Chessgames.com|access-date=2020-09-16}}</ref> between [[Lajos Portisch]] and [[Viktor Korchnoi]] in Belgrade in the [[USSR_and_Russia_versus_the_Rest_of_the_World#First_match,_Belgrade_1970|Russia (USSR) vs. Rest of the World 1970]] match.  After 21...Qb5 ({{em|see diagram}}), in a clearly better position,{{refn|"22. Bf1 White steers for a repetition and a draw. Modern engines evaluate the position as clearly better for White." per ChessBase article<ref name="ChessBasePortisch">{{cite web|last=Fischer|first=Johannes|date=14 April 2020|title=USSR vs. Rest of the World, 1970: Lajos Portisch comments|url=https://en.chessbase.com/post/ussr-vs-rest-of-the-world-1970-lajos-portisch-speaks|url-status=live|archive-url=https://web.archive.org/web/20200915112234/https://en.chessbase.com/post/ussr-vs-rest-of-the-world-1970-lajos-portisch-speaks|archive-date=15 September 2020|access-date=15 September 2020|publisher=Chessbase}}</ref>}} Portisch allowed this position to repeat three times and was criticized by teammate [[Bobby Fischer]] for allowing it.<ref>{{harvcol|Brady|1973|p=163}}</ref> If Portisch had won the game, the match would have been a tie. Play continued:

:'''22. Bf1 Qc6'''
:'''23. Bg2 Qb5''' (second time)
:'''24. Bf1 Qc6'''
:'''25. Bg2 ½-½'''
allowing Black to claim the threefold repetition with 25...Qb5.
{{clear}}