Yagoda had not shown much enthusiasm for the show trials and dismissed them as "nonsense".
Stalin believed in the show trials and wanted an escalation in the level of state terror in order to consolidate his political control and Yezhov shared this vision.
Yezhov had undermined Yagoda behind the scenes by cultivating a strong relationship with Stalin.
He was totally loyal to Stalin, who called Yezhov his "blackberry".
Yezhov was a workaholic who was initially popular with the most of the leading Party members.
Yezhov oversaw the most bloodthirsty period of the Terror, earning himself the nickname of the "poisoned dwarf" at 4ft 11 inches.
The period of 1936-38 over which Yezhov lead the NKVD is known as the "Yezhovschina".
Yezhov admitted that the wave of Terror about to be unleashed would result in many innocent victimes.
"We are launching a major attack on the enemy. Better than 10 innocent people should suffer than 1 spy get away."
In July 1937, Yezhov drew up an arrest list of 250,000 "anti-Soviet elements" including scientists, writers, musicians, administrators and managers.
Yezhov implemented the quota system whereby each region had to arrest a certain number of "enemies of the people".
Yezhov even stated that 28% of those arrested should be shot while the remainder should be sentenced to 10 years hard labour.