Leningrader Sophia Petrova in 1941, and showing the ravages of starvation in 1942
The city on the Neva was one of the Germans' main strategic targets. Such was the speed of Army Group North's advance that by the end of August they had reached Leningrad, and within days had cut off all land approaches to it.
Did Hitler really intend, as he promised, to raze it to the ground? Would ideological motives have taken precedence over the benefits of gaining control of its huge productive capacity? Quite possibly, not least because Soviet scorched earth policy would have left of little of value to the Germans.
Stalin, however, was determined to hold the city at all costs. The collapse of the Leningrad front would make Moscow, whose outer defences the Wehrmacht was rapidly penetrating, still more vulnerable; and its loss would deprive the Red Army of vital weapons and munitions.
Georgii Zhukov was dispatched to galvanise Leningrad's demoralised defenders. He did so with such effect that Hitler abandoned the idea of taking the city by storm. Now the plan was to starve it into surrender.
The result in winter 1941-2 was the worst famine ever in a developed society. Two and a half million people were trapped in Leningrad. With low reserves of food and fuel, only a trickle of supplies, and rations at starvation level, without heating or lighting, running water or drainage, and exposed to one of the bitterest winters on record as well as to continual bombing and shelling, they died in appalling numbers.
By the time spring came, half a million people were dead. Altogether around a third of the population would die during nearly 900 days of siege, a third would be evacuated, and a third would remain.
Stalin has been accused of sacrificing Leningrad, of indifference to its population's fate, with some justice. For him the needs of the Red Army had total priority. This is why the evacuation of civilians by the ice road across Lake Ladoga was delayed for weeks.
A large-scale air-lift of food into the city could have saved many lives, though it would have diverted planes from the military campaign. And while thousands were dying every day, news about Leningrad's ordeal was totally censored.
Nonetheless, the Soviet authorities got supplies through to the starving city, got people out, kept morale from collapsing, and eventually lifted the siege. Some of the credit for this belongs to Stalin. What is also certain is that Leningrad's fate would have been far worse had the city fallen to the Nazis.
The Leningrad Affair
Kuznetsov (left) and Zhdanov were heroes of the Leningrad siege, but a threat to Stalin
In the immediate aftermath of war, Leningrad's fortunes revived. Substantial resources were allocated to the huge task of restoring the shattered infrastructure of the city and its surroundings. Its heroism was praised and a museum to commemorate the siege opened.
Zhdanov was recalled to Moscow to become, by 1946, the leading figure in the party hierarchy after Stalin himself. His former deputy, AA Kuznetsov, was also brought to Moscow as a secretary of the Party Central Committee. Another Leningrader, NA Voznesensky, was now in charge of planning the Soviet economy and deputy chairman of the Council of Ministers.
But Stalin was well aware of the distinctive ethos that three years of relative autonomy from Moscow had fostered in Leningrad; and his suspicions were fed by two of the main contenders for power, Lavrentii Beria and Georgii Malenkov.
In 1946 Stalin gave Zhdanov the task of denouncing two of Leningrad's leading writers, Anna Akhmatova and Mikhail Zoshchenko, as part of a vicious campaign against 'bourgeois formalism' in Soviet culture known, unfairly, to history as the Zhdanovshchina.
In spring 1948 his son, a Central Committee official, was severely criticised for ideological errors. There were signs that Zhdanov himself was falling from favour, when in August he suffered a massive heart attack and died.
This tipped the balance in the Kremlin power struggle. Deprived of Zhdanov's protection, Kuznetsov, Voznesensky, Leningrad's current leaders, PS Popkov and YF Lazutin, and former Leningrad officials including MI Rodionov, prime minister of the Russian Republic, were arrested on trumped-up charges in 1949.
After long interrogations and brief secret trials, they were shot in October 1950. The Leningrad party organisation was purged, and some 2,000 people imprisoned or exiled.
The siege museum was closed, to be reopened 40 years later. For many years Leningrad's tragic and heroic wartime history would be barely acknowledged, and important aspects of what happened remain unknown to this day.
The aging dictator
By the 1950s Stalin was in ill health, but the cult of personality surrounding him grew
The leading victims of the Leningrad Affair were the highest ranking figures to be eliminated in Stalin's last years, but it was only one of a series of purges of 'enemies of the people' within the party and state apparatus, culminating in the 'Doctors' Plot' of 1953.
While the scale of executions came nowhere near the Terror of 1937-9 - he had no desire to see the purge spiral out of control as it had then - this was in many ways the darkest period of the Stalin era.
Attributing this to the aging dictator's paranoia is part of the explanation. He was by now a sick man - the enormous strain of leading the Soviet war effort had taken its toll, and he suffered a stroke in autumn 1945.
He spent months each year at his dachas by the Black Sea. Even in Moscow he left it to others to preside at the Council of Ministers or Secretariat of the Party Central Committee. The day-to-day running of the party and state machine was increasingly in the hands of men like Malenkov, Khrushchev, Beria and Bulganin.
Stalin retained control through the continuous flow of information, his monopoly of secret intelligence and his immense authority - in these years his cult of the personality reached its apogee. He was all too aware of his failing powers, and this made him all the more likely to intervene, with potentially devastating effect, in the political process.
But not only this. The post-war Soviet Union faced major economic and social problems, soon in the dangerous context of the Cold War. Labour productivity was low, living conditions for many abysmal. There was a serious shortage of manpower (27 million had died in the war), and key areas of science and technology lagged behind the West. The younger men around Stalin were beginning to look for new solutions, as well, inevitably, as to think about the succession.
The dictator's response was to turn to tried and tested methods of the past - control, vigilance, dogma, repression - to preserve what he had created and his own power. Had he lived longer, like his admirer Mao Tse-Tung, he might well have plunged his country into a mass campaign to eliminate all threats to the victory of Communism.
Fortunately for the Soviet people fate intervened. On 1 March 1953, Stalin suffered a massive stroke. Due in part to the deliberate inactivity of his closest comrades, he died five days later at the age of 74.
Within hours they had begun demolishing their master's legacy. And among their first actions would be the reinvestigation of the Leningrad Affair, leading to its denunciation as pure fabrication.