OGPU
According to Simon Sebag Montefiore, Stalin regarded Tukhachevsky as his bitterest rival and dubbed him "Napoleonchik" (little Napoleon). Upon Stalin's ascension to Party leadership in 1929, he began receiving denunciations from senior officers who disapproved of Tukhachevsky's tactical theories. Then, in 1930, the Joint State Political Directorate forced two officers to testify that Tukhachevsky was plotting to overthrow the Politburo via a coup d'état.