disagreement over the policy between Litvinov and Molotov about how to attain that goal, and Stalin alternated between their positions, initially pursuing both contradictory lines simultaneously quite early and abandoning collective security only at some point in 1939. Nazi Germany started its quest for a pact with the Soviet Union at some point in the spring of 1939 in order to prevent an English–Soviet–French alliance and to secure Soviet neutrality in a future Polish–German war. Some argue that the rapprochement could start as early as in 1935–1936, when Soviet trade representative in Berlin David Kandelaki made attempts at political negotiations on behalf of Stalin and Molotov, behind Litvinov's back. Molotov's speech to the Central Executive Committee of the Supreme Soviet in January 1936 is usually taken to mark this change of policy. Thus, Litvinov's anti-German line did not enjoy unanimous support by the Soviet leadership long before his dismissal. Walter Krivitsky, an NKVD agent, who defected in the Netherlands in 1937, reported in his memoires in 1938 that already then Stalin had sought better relations with Germany. According to other historians, these were merely responses to German overtures for détente. It is also possible that the change of foreign policy occurred in 1938, after the Munich Agreement, which became the final defeat of Litvinov's anti-German policy of collective security, which was marked by the reported remark about an inevitable fourth partition of Poland made by Litvinov's deputy Vladimir Potemkin in a conversation with French ambassador Robert Coulondre shortly thereafter. The turn towards Germany could also have been made in early 1939, marked by Stalin's speech to the 18th Congress of the Communist Party of the Soviet Union in March 1939, shortly after the German occupation of Czechoslovakia, when he warned that the Western democracies were trying to provoke a conflict between Germany and the Soviet Union and declared the Soviet Union's non-involvement in inter-capitalist quarrels, which is sometimes considered to have been a signal to Berlin. According to others, the first sign of a Soviet–German political détente was the conversation between Soviet ambassador Aleksey Merekalov and Ernst von Weizsäcker, State Secretary in the German Foreign Ministry, on April 17, 1939, when the former hinted at possible improvement of the relations. This was followed by a series of perceived German signals of goodwill and the replacement of Litvinov with Molotov. According to Geoffrey Roberts, recently released documents from the Soviet diplomatic