Hundreds of thousands of Russians starved to death in Leningrad because Stalin refused to allow them to evacuate. Leningrad was never cut off from supplies. At the height of the siege supplies were being trucked across Lake Ladoga in large quantities. Every empty truck could have carried forty civilians to safety, but Stalin wouldn't allow it, it was bad propaganda. In the winter it was trucks, in the summer it was barges and boats. Hell, Stalin was shipping large amounts of steel aluminum and supplies to make ammo during the siege, the tank factories in Leningrad never stopped producing tanks.