At the beginning of his chess career, around 1930, Najdorf defeated a player believed to be named "Glücksberg" in a famous game often referred to as "The Polish Immortal".
In 1935, he tied for 2nd–4th with Frydman and Henryk Friedman, behind Tartakower, in the 3rd Polish Chess Championship, held in Warsaw.
[5] In the 1939 Olympiad, Najdorf played second board for Poland and achieved a score of +12−2=4, winning a gold pen and pencil set.
[10] He set these records in the hope that the news would be reported in Europe and his family would learn of his whereabouts,[8] but they had perished in concentration camps by the time the information arrived.
In 1945, he won at Buenos Aires (Roberto Grau Memorial), with 10/12, ahead of Ståhlberg and Carlos Guimard.
[12] After World War II ended, organized chess resumed in the international arena, particularly in war-stricken Europe.
He then won at Prague, with (+9−1=3), ahead of Petar Trifunović, Gösta Stoltz, Svetozar Gligorić, and Jan Foltys.
He tied for 4th–5th with Héctor Rossetto at Mar del Plata, with 10/17, behind Eliskases, Ståhlberg, and Medina Garcia.
In 1950, he won at Amsterdam, with 15/19, ahead of Samuel Reshevsky (14), Ståhlberg (13½), Gligorić (12), Vasja Pirc (12), and Euwe (11½).
Najdorf stated in a 1947 interview: I believe that I am inferior to none of the players who are to participate in the next world championship, Botvinnik, Fine, Reshevsky, Keres, Euwe.
In the same year he played at Budapest in the Candidates Tournament to select a challenger for the World Chess Championship 1951, and finished fifth.
Najdorf's lively personality made him a great favorite among chess fans, as he displayed an aptitude for witty sayings, in the manner of his mentor Tartakower.
An example: commenting on his opponent at the 1970 USSR vs. Rest of the World match, he remarked, "When [then-World Champion Boris] Spassky offers you a piece, you might as well resign then and there.
He won the South African Open in 1976[17] and at age 69, he tied for second place in a very strong field at Buenos Aires 1979, with 8/13, behind winner Bent Larsen (11/13), though ahead of former world champions Tigran Petrosian and Boris Spassky.
He played first board in the 9th Chess Olympiad at Dubrovnik 1950 (+8–0=6), as well as at Helsinki 1952 (+11–2=3), Amsterdam 1954, Moscow 1956, Leipzig 1960, Varna 1962, Havana 1966, Lugano 1968, Siegen 1970, and Haifa 1976.
The Najdorf Variation in the Sicilian Defense, one of the most popular openings in modern chess, is named after him.
Najdorf was also a well-respected chess journalist, who had a popular column in the Buenos Aires Clarín newspaper.
When he was 14, he visited his school friend Ruben Fridelbaum's house, and his violinist father taught him chess.
Mikel was immediately hooked, read books about the game, and was soon able to give his teacher rook odds.
When Najdorf boarded the ship for the Buenos Aires Olympiad in 1939, Genia was ill with influenza, and chose not to accompany him.
His parents, wife and baby daughter,[19] and all his known relatives and friends, were murdered in The Holocaust including his father.
[20] However, many years later, by chance he met a Polish immigrant in the New York City Subway, who turned out to be a cousin.
[9] In April 1947, Najdorf met Adela ("Eta"), one of the youngest of three daughters of Russian Jewish immigrants Isaac and Esther Jusid.
She describes her father as a mixture of extremes: violent-tempered, but compassionate and loving, selfish at times but also generous to a fault, jovial and a bon vivant, but also sad because of the terrible losses of the Holocaust.
Najdorf had met Rita and her husband Jacobo, a socialist attorney and keen chess player, soon after he arrived in Argentina.
After Adela died, Rita and Najdorf became a couple, which Miguel's daughters accepted without surprise and with relief.