You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
alternatehistory.com
In several history books and atlases (John Keegan's being one of the few I can list of the top of my head), there are mentions of a possible capture of Leningrad in late July when its defenses were disorganized via a rapid thrust.
The reason why such a thrust did not occur before Leningrad reorganized to a solid endurance siege was apparently because Hitler insisted on diverting forces to help Army Group Center assault Moscow.
Here's a map to draw a surfer's interest:
So, what if Leningrad was able to be taken in that apparently critical month?
It'd be clearer if someone lists the short-term effects (the rest of the operation) and the long term effects (entire eastern front).