Beginning in the summer of 1938 a coalition of Politburo members, reportedly consisting of Zhdanov, Andreev, Kaganovich, Mikoyan, and Molotov, worked to limit Yezhov’s and the NKVD’s powers. In August, Beria was appointed Deputy People’s Commissar of the NKVD without Yezhov’s consent. During the fall, the Politburo restricted the NKVD’s power somewhat and appointed a series of commissions to investigate NKVD operations, arrest procedures, and Yezhov’s performance. The most dramatic move came on 17 November 1938, when it criticized aspects of the NKVD’s work, abolished its troikas that had summarily sentenced so many to death or hard labor, and condemned its excesses. On 23 November 1938, Yezhov submitted his resignation as NKVD chief to Stalin. The Politburo accepted it and replaced him with Beria. Yezhov retained his other party and state positions until he was arrested in April 1939. He was executed on 4 February 1940.

Chase, William J., Enemies Within the Gates?, translated by Vadim A. Staklo, New Haven: Yale University Press, c2001, p. 306.

It was Beria’s diagnosis of the danger of Yezhov’s excesses that had induced Stalin to trust him and brought him to power. Throughout the country these excesses had cast their shadow. At one sitting alone, the Central Committee of the Azerbaizhan Party had expelled 279 members, the Ukrainian Stalinsk Provincial Committee 72, the Ordjonikidze Regional Committee 101–it was the same everywhere…. The fear of being suspected of lack of vigilance drove local fanatics to denounce not only Bukharinists, but also Malenkovists, Yezhovists, even Stalinists. It is of course not impossible that they were also egged on to do so by concealed oppositionists! Hence Beria’s task when he was summoned from Georgia by Stalin was to head a secret commission of inquiry into Yezhov’s work.

To give Beria his due, he pulled no punches. At a closed joint session of the Central Committee and the Central Control Commission of the Party, held in the autumn of 1938, he declared that if Yezhov were not a deliberate Nazi agent he was certainly an involuntary one. He had turned the central offices of the NKVD into a breeding ground for fascist agents. He had scorned citizens’ constitutional rights and used illegal methods of extorting information, to such an extent that he had set quite non-political people against the Government. For a rank-and-file member of the Central Committee to say this was the height of courage.

The impression produced on Stalin and Molotov was tremendous. The Central Committee resolutions dismissing Yezhov (Member of the Politburo, the Orgburo, and the Presidium of the Supreme Soviet, Secretary of the Central Committee, and People’s Commissar of Internal Affairs; were written in Beria’s hand. Beria’s first acts as head of the NKVD, were the arrest of Yezhov and the issue of orders quashing an enormous number of sentences and recently-started proceedings. People who had been unjustly repressed were even indemnified by the State. Special commissions inquired into the past of convicted persons.

Tokaev, Grigori. Comrade X. London: Harvill Press,1956, p. 119

Evgeniia Ginsburg, who was in Yaroslavl Prison and who saw no newspapers, said that the prisoners could tell when Yezhov fell: The draconian regime in the prisons (frequent solitary confinement and deprivation of all privileges) was relaxed one day. The timing was confirmed a few days later when Beria’s name began to appear on official prison notices.

Getty, A. Origins of the Great Purges. Cambridge, N. Y.: Cambridge Univ. Press, 1985, p. 189

… the replacement of Yezhov by Beria was received as a hopeful sign. And in fact, right after Yezhov’s replacement mass repression was discontinued for a while. Hundreds of thousands of cases then being prepared by the NKVD were temporarily put aside.

Medvedev, Roy. Let History Judge. New York: Columbia University Press, 1989, p. 465

KGB Deputy Chairman Vladimir Pirozhkov (I think) makes a public comment including Beria as one of the officials sentenced for violations of Soviet Law.

When asked about the fate of the perpetrators of the repressions and about the statute of limitations, Solomontsev answered:

“With regard to those instances of violations of socialist legality in the ’30s, ’40s, and early ’50s that have been revealed, the culprits have already been punished through criminal, legal, and party channels. It is obviously not a secret to everyone that Avakumov, Ryutin, Leonov, Komarov, Likhachev, Shvartsman, and other former leaders and personnel of the USSR Ministry of State Security were sentenced to death for fabricating investigation materials….”

Even more amazing was an interview given by Pirozhkov, deputy head of the KGB. When asked how many hangmen had been brought to trial, he answered that 1,342 NKVD officials had been sentenced for severe violations of socialist legality, including Beria, Yezhov, Kobulov, Frinovsky, Agranov, Avakumov and others.

Laqueur, Walter. Stalin: The Glasnost Revelations. New York: Scribner’s, c1990, p. 266