An alternate timeline by Althistorian 2005.
The traditional narrative is that in mid-1941, Japanese leaders were split between the “strike north” faction, championed by the Imperial Army, which wanted to attack the Soviet Union. Opposing them was the Navy-backed “strike south” faction pressing for seizing the resources of Southeast Asia from their American and European masters.
So what if the "strike-north" faction won and Japan attacked the Soviet Union instead of Pearl Harbor?
1941: On 22 June, Nazi Germany activates Operation Barbarossa and attacks the Soviet Union. Towards the end of the year, Japanese leaders decide to assist their ally, and the Japanese army storms into eastern Siberia. The Soviets end up having to keep their elite Siberian troops in Siberia to fight the Japanese, allowing Hitler to take Moscow before his armies freeze in the Russian winter and hold their positions before defrosting the next spring. Stalin is captured, but his generals and the Politburo (Soviet Congress) are determined to continue fighting and eventually free him.
1942: With Moscow captured, Leningrad finally collapses, lowering Soviet morale even further. Despite the elite Siberian units moving back to western Russia and leaving Siberia to the Japanese, they fail to make a difference and are moved back, but not before losing plenty of Siberian territory and soldiers' lives. Eventually, the victorious Wehrmacht enters Stalingrad, and the oil-rich Caucasus region falls into German hands. The Soviets finally sue for peace and the Axis gain the plentiful resources of the Siberian wilderness. Despite this, however, the British keep fighting and continue pleading with the USA to join the war.
1943: With the Soviet Union destroyed, the Japanese finally strike south, attacking Pearl Harbor and the Philippines, causing America to join the war. The British are saved from suing for peace, and the war continues. Meanwhile, the Wehrmacht is moved back to France to prepare for Operation Sealion (the invasion of Britain), and when the British find out, they invade Persia (with little to no resistance) and attack the Caucasus from there, opening the Caucasian Front.
1944: With American assistance, the British begin preparing to push Axis forces out of Africa. ￼Eventually, landings are made, and North Africa is liberated from the Afrika Korps of Generalfeldmarschall Erwin Rommel. Afterwards, preparations begin for the invasion of Italy as well as the liberation of Normandy. Meanwhile, American troops land in Siberia and clash with Japanese units, reopening the Eastern Front.
1945: Allied forces land in Italy, causing Italian dictator Benito Mussolini to be deposed by his own government and also causing Italy to fall into civil war. Towards the end of the year, the US Army storms into Manchuria and Korea, encouraging Chinese guerilla fighters to expel Japanese troops from China.
1946: In early March, the invasion of Normandy succeeds, opening up yet another front for the Nazis to deal with. Most of Southeast Asia is successfully liberated from the Japanese, despite their dogmatic resistance. American reinforcements are also sent to help the British army on the Caucasian Front.
1947: A massive offensive takes place, pressuring the German army from all fronts. The Manhattan Project is finally completed, with A-bombs being dropped on both Berlin and Hiroshima. Hitler is killed and his commanders surrender. The Japanese make peace and are dealt with the same way as in OTL, while Korea gains independence as a unified democratic nation. Germany and Austria, as well as Berlin and Vienna are both divided into British, French, and American sectors, while Axis-occupied nations have their pre-war governments restored. The Versailles Treaty is revised to prevent another World War, allowing Austria to unite with Germany after the Allied occupation ends. Other Axis allies such as Romania, Bulgaria, and Hungary hold free elections to choose new governments. Italy become a republic and is forced to give independence to Ethiopia, which gains the rest of Italian East Africa along with their own territory. World War 2 is over.
Without a Soviet communist threat to divert British and French (but also Dutch, Belgian, and Italian) forces back to Europe, most colonies initially remain colonised except for British Palestine, which is divided into the Arab state of Palestine and the Jewish state of Israel. Unlike in OTL, a peaceful solution is achieved and both countries are able to coexist with each other. India still gains independence despite the best efforts of the British government to stop Gandhi, apartheid and segregation end faster in South Africa and the US respectively, and Indonesia gains independence from the Netherlands despite their military defeat.
Slowly, the old colonial empires erode away anyway due to the war causing massive damage that they simply can't afford to repair while still holding on to their colonies. Thus, many colonies are slowly granted independence peacefully, avoiding the many civil wars and coup d'etats that would otherwise plague Africa. America also grants independence to the Philippines.
In 1979, a revolution in Persia (now called Iran) is averted by liberal reforms that the US president wouldn't have allowed the Shah to enact had there been a communist threat in the north.￼ An unified Arab state is also formed, but as a secular (although still conservative) constitutional monarchy instead of an ultraconservative absolute Islamic monarchy. In China, the Nationalists win the Chinese Civil War in 1951 due to the Communist Party losing their popular support following the Soviet defeat in World War 2. International aid slowly helps the Chinese economy recover from the Chinese 'Century of Humiliation', especially the opium trade.