It is estimated that around 1.5 million civilians died (mostly from starvation) during the Siege of Leningrad (mostly during the harsh winter of 1941/42). Although the Wehrmacht almost completely encircled Leningrad by September 8th, 1941, the key word is “almost”.
In reality, there was no such thing as “Blockade of Leningrad” because the term “blockade” assumes that the object in question is encircled completely – no one and nothing can get in or out except by air.
During the Siege of Leningrad that lasted for 872 days (it was completely lifted only on January 27th, 1944), the city was never encircled completely. There was always a way to get in and out a significant number of people, supplies and military goods produced by Leningrad factories.
Contrary to a very popular misconception, the Soviet High Command possessed enough food and other vital supplies, transportation (i.e. ships and boats) and military aircraft (fighters) to supply Leningrad with everything necessary and sufficient to survive even an extremely harsh winter.
It was not done for but one reason – Stalin believed that Leningrad will fall (with or without this support) and thus considered that these vital supplies must be used elsewhere.
Consequently, the besieged city did not receive enough supplies to feed and otherwise support its residents. Not because there were none or they could not be delivered, but because Joseph Stalin personally decided to deprive the residents of Leningrad of these vital goods.
Therefore, the person truly responsible for 1.5 million dead during the Siege of Leningrad (the only true perpetrator of this monstrous crime) was not Adolf Hitler (as it is erroneously believed) or even Field Marshal Wilhelm Ritter von Leeb who commanded the Wehrmacht troops laying siege to the city (Army Group North), but the leader of the Soviet Union Joseph Stalin.