[1] He wrote books about Czech political trials during the 1950s, the situation of Jews in Central Europe during World War II, and the Communist takeover in Czechoslovakia.
During the Prague Spring in 1968, he worked for the Committee of Rehabilitation where he was able to access classified documents of the Czechoslovak Communist Party.
[1] After his exile he published documents on secret Soviet activities,[2] which were serialised in the Italian magazine Panorama.
[3][4] Kaplan claimed he had discovered files that described a secret meeting in the Kremlin in January 1951, where Joseph Stalin announced his plan for a war with the United States within three or four years, with the aim of driving the Americans out of Europe.
[3] In 1990, Kaplan returned to Czechoslovakia and continued his academic research in Prague.