Before we start this History Extra podcast, we want to tell you a bit about this week's sponsor, Warner Hotels.

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Welcome to the History Extra podcast, fascinating historical conversations from the makers of BBC History Magazine.

Throughout the 1930s, Winston Churchill was among the Soviet Union's fiercest critics,

while Joseph Stalin viewed the British with contempt.

Then, when Hitler invaded the Soviet Union, everything changed.

Giles Milton has written a book on the subject, and here in conversation with Spencer Mizzin,

he explores how Churchill and Stalin, alongside US President Franklin D. Roosevelt, formed a fractious, explosive, but ultimately

war-winning alliance.

You're a new book.

You begin it by describing the scene on the morning of 22nd of June, 1941, when Winston Churchill

receives the news that Nazi Germany has launched a massive invasion

of the Soviet Union. Now, this news, as you tell us, elicited from Churchill a smile of satisfaction

and the lighting of a celebratory cigar. So why exactly was the British Prime Minister so pleased

that Hitler had launched this enormous invasion of the Soviet Union?

Well, hi Spencer. This was a key point in the early years of the war. In fact, it was a major

turning point as far as Churchill was concerned,

...