This tournament played to determine a new World Champion because Alekhine had died in 1946. The tournament marked the passing of control of the championship title to FIDE and not the title holder. Botvinnik won the five-player championship tournament, beginning the era of Soviet domination that would last over twenty years. The tournament was played partly in The Hague and partly in Moscow.
FIDE found it very difficult to organize because problems with money and travel so soon after the end of World War 2 prevented many countries from sending representatives. The result was rumors and speculation ran rampant.
1938 AVRO tournament was used as the basis for the 1948 Championship Tournament. FIDE decided that the other six participants at AVRO would play a quadruple round robin. The players were Euwe, Botvinnik, Keres, Flohr (now from the USSR), Fine and Reshevsky. The Soviet Union chose to replace the fading Flohr with a young player who had emerged during the war years and was obviously stronger named Vassily Smyslov. Reuben Fine elected not to play and there was a proposal that he should be replaced with Miguel Najdorf but in the end the tournament was played with only five players: Euwe, Smyslov, Keres, Botvinnik, and Reshevsky
Before the tournament, Botvinnik was considered the favorite because of his victory at Groningen 1946 and his pre-war results. Keres and Reshevsky were veterans of international competition and although Euwe was the former world champion, he had played poorly since Groningen. Smyslov was not well known in the West, as he had only appeared in two international competitions: a third place finish at Groningen and shared second at Warsaw 1947.
The Soviets brought a large contingent of about twenty-one including the players Botvinnik, Keres, and Smyslov; their seconds Ragosin, Tolush and Alatortsev. Also included in the gaggle of the Soviet contingent were Bondarevsky, Flohr and Lilienthal as correspondents and member of the adjudication committee, Kotov. The leader of the group was Postnikov, a private doctor from Moscow and Botvinnik's wife and young daughter. On the other hand, the US delegation consisted of one person: Reshevsky. Dutch player Lodewijk Prins was gotten at last moment to be his second. Former world Champion Euwe’s second was Theo van Scheltinga.
Botvinnik won the tournament convincingly with 14 points out of 20. He also had a plus score against all the other players. Smyslov came second with 11 points, just ahead of Keres and Reshevsky on 10½. Former champion Euwe was in bad form, and finished last with 4 out of 20.
There was some controversy when Paul Keres lost his first four games against Botvinnik raising suspicions that Keres was forced to throw games to allow Botvinnik to win the Championship. Chess historian Taylor Kingston investigated all the available evidence and arguments, and concluded that Soviet chess officials gave Keres strong hints that he should not hinder Botvinnik's attempt to win the World Championship. Supposedly Botvinnik discovered this about half-way through the tournament and protested so strongly that he angered Soviet officials. In later years Samuel Reshevsky stated his opinion that Keres’ play was not steady enough to have ever won the world championship.
Read about the controversy HERE and HERE.