[3] Recalled to Moscow in November 1956, Leonov was discharged from the foreign service and deciding to pursue a career as a historian of Latin America, went to work as a translator for the official Soviet Spanish-language publishing house, Editorial Progreso.

During the October 1962 Cuban Missile Crisis, he received regular reports from agents in Florida with respect to American military preparations.

A report compiled by his office in 1975 recognized the growing peril to the power of the Soviet Union in geopolitical terms, arguing that in keeping with the policy of the British Empire before it, the Soviet Union should limit the commitment of its resources to a few key areas from which its power could operate in a more selective fashion.

The report suggested establishing a Soviet foothold on the Arabian Peninsula in "the most Marxist country" in the region, South Yemen.

In the late 1970s and the early 1980s he traveled frequently to Poland to assess the situation and reportedly told the head of the KGB Yuri Andropov, in a heated discussion, that the prospects of Polish socialism looked bleak.

In December 2003, Leonov was elected to the State Duma, the lower house of the Russian parliament, as a member of the nationalist Rodina party.