By the spring of 1939 Adolf Hitler’s Third Reich and Joseph Stalin’s USSR had been “pouring buckets of shit on each other’s heads” for decades, as Stalin later said.

During the 1920s and 1930s they vied for power in Europe, blaming each other for all economic and social ills, and battling through proxies in the Spanish Civil War. Their diametrically opposed far-left and far-right philosophies and economic strategies culminated in the German-led Anti-Comintern Pact of 1936-37 creating an alliance between the Third Reich, Imperial Japan and eventually Benito Mussolini’s Fascist Italy against the spread of Communism, and more specifically the threat of a Soviet invasion.

Early on, Hitler had feared that the USSR and the Western democracies would make an anti-Nazi alliance to curtail German expansion. He gave them three chances to do so, and they flubbed them all. In 1936 when Hitler “remilitarized” the Rhineland, an extant Russia-France pact could have been called into play and both countries could have invaded Germany. France did not insist on doing so, and its similar reluctance to pincer the Third Reich allowed Hitler’s Anschluss with Austria in early 1938 and the Nazi occupation of the Sudetenland part of Czechoslovakia that followed the Munich Accord in October 1938.

Stalin was irate at being excluded from the Munich talks. His absence allowed Britain’s Neville Chamberlain and France’s Edouard Daladier, urged on by Mussolini, to hand the Sudetenland to Hitler without Russian objections.

Stalin blamed Soviet Foreign Secretary Maxim Litvinov, a Jew born Meir Henoch Wallach of Bialystok, for being boxed out of Munich. Until then, Litvinov had done very well by the USSR and by Stalin. An old-line Communist who prior to the Revolution had spent time in jail and in exile in the party’s service, in 1921 he had been appointed by Vladimir Lenin as deputy commissar for foreign affairs, and after Lenin died, in 1930 Stalin had elevated Litvinov to the top position. He then succeeded in getting formal recognition of the USSR by the United States of America and acceptance into the League of Nations; he also birthed the non-aggression alliances with Latvia, Estonia, Lithuania, Poland, and Turkey that provided the USSR with a border of buffer states against a German invasion.

But as the Nazis continued to expand the Third Reich, Stalin became convinced that the buffer states were not enough protection for the USSR at just the moment when it could not sustain a war because his purge of the Soviet military had left it too weak for large-scale combat.

“ Hitler’s hatred for Jews was well known, and for some time his minions had been complaining to Stalin’s about their chief negotiator, the Jew whom they referred to as ‘Litvinov-Finkelstein.’ ”

Hitler, for his part, had been vocally anti-Soviet until he began listening to former Champagne salesman Joachim von Ribbentrop. Married to a wealthy woman and known for lavish spending, pretensions, and incompetence, von Ribbentrop joined the Nazi Party in 1932. He steadily gained traction in the foreign ministry by loudly opposing the foreign minister, Konstantin von Neurath, with the aid of the Schutzstaffel, better known by the initials SS—Ribbentrop liked to wear his SS general’s uniform for diplomatic occasions, even as ambassador to Great Britain.

Hitler had steadily become disenchanted with von Neurath and a foreign ministry that slow-walked every bold stroke he attempted. So after shaking up the German military, in early 1938 Hitler upended the foreign ministry and appointed von Ribbentrop as top dog. The salesman had already begun selling Hitler hard on the attractiveness of a pact with the USSR: in case of war it could prevent the Third Reich from having to fight on two fronts, and could assure continued access to raw materials—grains, soybeans, oil, and phosphates—in the likely event of a British and French naval blockade of Germany.

Hitler’s hatred for Jews was well-known, and for some time his minions had been complaining to Stalin’s about their chief negotiator, the Jew whom they referred to as “Litvinov-Finkelstein,” implying that great progress could be made between the two countries if he was removed.

Stalin sacked Litvinov on May 3. He was arrested by the NKVD, his phones cut, his office locked, his aides interrogated. Too prominent in the West to be summarily executed, he was dispatched to Washington, D.C., as ambassador, and Stalin replaced him as foreign secretary with his most loyal protégé, Vyacheslav Molotov.

As with the name ‘Litvinov,’ ‘Molotov’ was a Revolutionary moniker. In Russian it meant “the hammer,” and he functioned as the hammer to Stalin’s sickle. When informed that his Party colleagues called him Comrade Stone-ass for his ability to sit through interminable meetings, Molotov corrected them by saying that Lenin himself had dubbed him Comrade Iron-ass.

The switch of Molotov for Litvinov was an unmistakable signal that collective security via the USSR’s alliances with buffer states and Western democracies was dead. And Hitler had already sent another unmistakable signal: that his next target was the German-speaking area of Poland known as the Danzig Corridor.

Did the Western democracies miss these signals and the potential for a Hitler-Stalin alliance? No, but fear of confrontation, based on the terrible experience of the Great War, and the lack of bloodshed so far in Hitler’s take-overs had lulled them into complacency.

“ Territory grabs were the essence of the ‘secret protocol’ that Molotov would continue to deny until his dying day, and that Vladimir Putin shrugged off as fake news. It gave the Soviets carte blanche in the Baltic states and the eastern half of Poland. ”

But the dictators were ready to act. On May 17, a Russian attaché in Berlin told his German counterpart that there were no foreign policy conflicts between the two countries. As von Ribbentrop would shortly put it in a missive to Moscow, “There is no question between the Baltic and the Black Sea which cannot be settled to the complete satisfaction of both [Soviet and German] parties.”

London and Paris did not react as quickly. As though there were no urgency, their first delegation did not arrive in Moscow until June 15, and it was half-hearted: military officials only authorized to make tentative commitments, subject to ratification at home. They conveyed that Great Britain and France would indeed give the USSR a free hand in the Baltic States and Finland, and the right to enter Poland and Rumania—but only if Germany invaded Poland or Rumania.

Hitler could offer the USSR the same territorial conquests, and without having to fight Nazi Germany to obtain them.

Those territory grabs were the essence of the “secret protocol” of the eventual Nazi-Soviet pact, a few paragraphs whose existence would not be acknowledged until the Nuremberg Trials of 1945, that Molotov would continue to deny until his dying day, and that Vladimir Putin shrugged off as fake news. It gave the Soviets carte blanche in the Baltic states and the eastern half of Poland.

After three months of incremental progress produced a draft document that both sides liked, on Aug. 21 a Stalin telegram arrived in Berlin authorizing von Ribbentrop to fly to Moscow on Aug. 23. As von Ribbentrop’s motorcade was making its way from the airport to the Kremlin, he was astonished to pass through streets lined with cheering Russians waving swastika flags and other Nazi banners. The flags and banners had been confiscated from a nearby film studio that had been making an anti-Nazi propaganda film. The film was never completed.

Negotiations went so well that von Ribbentrop was stunned. He had to phone for instructions regarding a hitch over who would gobble up what portions of Latvia. Hitler consulted a map and phoned back with a concession to Stalin.

“ On September 1, 1939, Hitler’s forces invaded Poland, their supreme commander secure in the knowledge that Soviet forces would not oppose them. ”

Once von Ribbentrop and Molotov had signed the pact, the German phoned again to Obersalzberg, Hitler’s mountain retreat, where he was readying the Poland invasion plans with the senior military staff. It was three in the morning. Architect Albert Speer was in the room as Hitler took the call: “Hitler stared into space for a moment, flushed deeply, then banged on the table so hard that the glasses rattled, and exclaimed in a voice breaking with excitement, ‘I have them! I have them!’”

In the next moments, he green-lit the invasion of Poland for September 1, having earlier postponed it so that the pact with the USSR could be signed. And he assured his generals that once they had occupied Poland and taken over France and the Low Countries, the Nazi juggernaut would overrun the USSR.

Stalin, in the Kremlin, was ecstatic, breaking out the Champagne and caviar, and toasting Hitler. Stalin had reason to gloat, for with a single stroke he had reassembled almost the entire Romanov Empire at the start of the Great War. Within months, 50 million more people in Estonia, Latvia, Lithuania, Poland, and parts of Finland would be under his control.

On Aug. 24, the public part of the non-aggression pact was publicized around the world. A few days later, Stalin managed not to mention the secret protocol part to a group of top aides when he told them that a war was about to begin “between two groups of capitalist countries for the redivision of the world, for the domination of the world! We see nothing wrong in their having a good hard fight and weakening each other. It would be fine if, at the hands of Germany, the position of the richest capitalist countries (especially England) were shaken.”

Even before von Ribbentrop returned to Berlin, an aide, Hans von Herwarth, quite upset over the secret protocol, gave a copy to his friend Chip Bohlen, then serving in the American embassy in Moscow. Bohlen reported this quickly to President Franklin D. Roosevelt, but the U.S. did not share the information with Great Britain or France prior to Sept. 1, 1939.

On that date, Hitler’s forces invaded Poland, their supreme commander secure in the knowledge that Soviet forces would not oppose them. France and Britain, although already mobilized, were nonetheless underprepared for the swiftness and ferocity of the German blitzkrieg. Other than declaring war they made rather minimal responses to the invasion of Poland, a country they had pledged to defend. Some French troops advanced east of the Maginot Line to the German border, but did not cross into Germany. British air raids did little damage. The naval blockade was begun, but did nothing to halt the advance of German troops.

In mid-September, after German troops reached the Polish capital, Warsaw, Stalin gave the go-ahead for Russian troops to enter Poland. Later he said that he was worried that the Germans would simply take the remainder of Poland if Russian troops did not claim that territory. The Russian Army’s entrance prevented 200,000 to 300,000 Polish troops from escaping to the south, where they might have survived in exile and served with the forces of the democracies.

When Britain and France learned of the Russian invasion, they pulled back the French troops from the German border to behind the Maginot Line, and ceased the air raids. By Sept. 28, 1939 Poland no longer existed. The first phase of World War II was over; the next phase would be dubbed “the phony war” because the belligerents appeared not to be engaging in active combat. That phase would end in May 1940 with Hitler’s invasion of France and the Low Countries.

When von Ribbentrop had gone to Moscow, Hitler had sent along his personal photographer, Heinrich Hoffman, to record the event and to bring back a photographic record of Stalin’s earlobes—if they hung loose from his head, then he was Aryan, but if they were attached, Stalin must be a Jew. Hoffman returned with close-ups that assured Hitler that Stalin’s earlobes were unattached—and that therefore, in Hitler’s eyes Stalin was a worthy partner, at least for the time being.