An ardently right-wing and royalist officer, he is notable for his involvement against the Centre Union party in the 1960s, which led to the political crisis of July 1965.

[1] In August 1944 he fled from occupied Greece to the Middle East, where he joined the armed forces of the Greek government in exile as a company commander.

[1] Gennimatas was widely regarded as an enemy of the Centre Union, and had been involved in the allegations of massive fraud in the 1961 parliamentary elections.

[2] Nevertheless, Gennimatas was chosen as the new Chief of the Army General Staff on 19 April 1964,[1] as part of a tacit agreement between Papandreou and King Constantine II that had allowed Papandreou to accede to the premiership in exchange for not interfering with the King's control over the armed forces.

[2][4] The political crisis culminated in the "Apostasy" of July 1965 – the defection of several Centre Union MPs, the dismissal of Papandreou and his replacement by a series of Palace-supported governments.