After managing to include baseball as a demonstration sport at the 1936 Berlin Olympics, Mann sought to organize an international tournament in 1937 between the national teams of the United States and Japan; this plan was derailed by the outbreak of the Second Sino-Japanese War that same year.

The 1938 "John Moores Cup," as it was originally called, would be retroactively recognized as the first Amateur World Series.

[6] Mann, along with Cuban sports administrator Jaime Mariné, helped turn the Amateur World Series into an annual event in 1939, this time held in Cuba.

[7][8] The first and second tournaments featured only two and three national teams, respectively, but seven participants were invited to the 1940 edition and the pool would only expand from there.

[12] Mariné had participated in the Cuban Revolution of 1933 that brought Batista to power and had organized the dictator's Military Intelligence Service in 1935.