This was formed during the Russian Revolution in 1915.
After the famine of 1915, people began to listen to the likes of Lenin and Trotsky. ultimately, they revolted, forcing the Tsar and his family into exile, seizing their property in the process (during the "sweeping away of the Tsar", Stalin was killed while trying to assassinate them, thus preventing the tyrannical regime of OTL). As a result of Lenin's death, Someone new took his place: Vyacheslav Molotov, who continued the NEP and allowed the churches to operate.
Second Great War
Japan, France and Britain simultaneously declared war on the Soviets. Germany joined the USSR in its struggle and several years later the triple Entente was beaten with US help.
After a botched attempt by Japan and Britain to crush the USSR, they turn to the United States and South Africa to form an alliance which would last to the present day. The Soviets would be a vital ally for the US and South Africa because of the massive oil reserves.
Third Great War
Britain had been helping Mexico modernize for the final war against America, and ditto with China.