The series was criticized for not mentioning that the UK broke its pact with Poland, and bombed Germany first on the night of 3rd September 1939. The RAF bombed German cities every night from 10th May 1940, four months before the Blitz started.
Adolf Hitler and Benito Mussolini's decision to declare war on the United States on 11 December 1941 is described in the series as a mistake. However it is likely that it made no difference. As the UK had declared war on Japan after the attack on Pearl Harbor, all restrictions on aiding Britain were off. It would only have been a short matter of time until German and Italian U-Boats began sinking American ships that were carrying arms and munitions to the UK, giving the US government its casus belli to declare war on Germany and Italy. Hitler and Mussolini could no longer ignore the vast amount of economic and military aid the US was giving to the Soviet Union and the British Empire. Some historians believe that Germany and Italy should have declared war on the US after the Destroyers for Bases Agreement in 1940. The US had officially abandoned its neutral stance in March 1941 with the beginning of Lend-Lease. American destroyers escorting convoys had already been de facto at war for months with German U-boats in the Atlantic, and Hitler's war declaration made Second Happy Time possible for U-boats.
Joseph Stalin intended to attack German forces in Eastern Europe by 1944. Adolf Hitler was aware of this and launched Operation Barbarossa on 22 June 1941 as a pre-emptive strike, before Stalin had time to fully prepare for war against the European Axis Powers. The Soviet offensive plans controversy suggested Stalin was preparing to attack the Axis in the summer of 1941.
Although the series claims that the United States was neutral until the attack on its naval base at Pearl Harbor, this was no longer true after the start of Lend Lease in March 1941. While not officially at war with the Axis, the US was enabling the British Empire and the Soviet Union to continue fighting. The US had also imposed an economic blockade against Japan in the summer of 1941.
The UK and France rejected a German-Soviet peace proposal on 28 September 1939. Adolf Hitler offered to end the war on 6 October 1939 following the German-Soviet conquest of Poland. Hitler offered to end the war with the UK in July 1940 following the Fall of France, and only authorized the bombing of RAF fighter bases in August after the British had already bombed German cities for three months. In May 1941 he again offered to end the war in the West if the British Empire did not interfere with Operation Barbarossa. Winston Churchill chose to reject Hitler's peace offers in 1940 and 1941.
Joseph Stalin deliberately waited until 17 September 1939 before launching his invasion of Poland, since he knew that the UK and France would not be able to declare war on the Soviet Union as well as Germany. The UK and France did consider declaring war following the Soviet invasion of Finland on 30 November 1939, as well as immediately bombing Baku to help the Finns.
The joint German-Soviet invasion of Poland was agreed in the Molotov-Ribbentrop Pact on 23 August 1939. Adolf Hitler could only invade Poland if Joseph Stalin did as well, otherwise Germany risked fighting a two-front war in 1939 before it had sufficiently rearmed. Stalin waited until 17 September before launching his invasion, knowing France and the British Empire would be unable to declare war on the Soviet Union as well as Germany.
Many historians believe Japan surrendered because of the Soviet Union's declaration of war on 9 August 1945 and simultaneous invasion of Manchuria. It has also been suggested that an Allied naval blockade would have been able to starve Japan into surrendering without the need for nuclear weapons.
The attack on the US naval base at Pearl Harbor was regarded as a war crime as the Japanese government did not declare war first. Declarations of war were rendered obsolete after World War II by the United Nations Charter. The Japanese had sent a message stating that negotiations with the US had been terminated, but there was a delay in its translation and it arrived half an hour after the attack had started.
Some historians have suggested there was no need for an invasion of Japan (Operation Downfall), and a naval blockade would have starved Japan into surrendering. It is believed Operation Starvation would have forced the country to surrender in the summer of 1945 if it had been started earlier.
Germany and the Soviet Union agreed to invade Poland in a secret protocol of the Molotov-Ribbentrop Pact, signed on 23 August 1939. In 1989 the Soviet government publicly apologized for the secret protocol.
The Royal Navy's blockade of Germany in both world wars was widely regarded as illegal under international law as it violated the Hague Convention of 1907. Admiral Erich Raeder said Germany's unrestricted submarine warfare was in response to the illegal naval blockade.
When Joseph Stalin offered to formally join the Axis Powers on 25 November 1940 he also requested that Axis forces should withdraw from eastern Europe. This threatened to cut off Germany's main supply of oil from Romania, and led Adolf Hitler to authorize planning for Operation Barbarossa on 18 December 1940.
The Battle of Midway was heralded as a turning point in the Pacific theater. However modern historians have asserted the battle made little difference, as Japan did not have the industrial capacity to simultaneously fight the United States, China and the British Empire. The Guadalcanal Campaign has also been called a turning point.