It is true there were other convoys that took heavy losses, but PQ-17 was by far the worse. Conversely, an awful lot of Arctic convoys were incredibly successful - I dont think a single ship was lost in the first ten that ran. And there were some where the casualties went the other way - convoy JW51B for example, which resulted in the battle of the Barents sea, where an attack by German surface units was most handily fought off by the escorts.
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