As a general comment I completely agree, flash. But in this instance there is a wealth of evidence demonstrating Soviet hostility to the supply flights. The Polish fighters were branded "criminals" and "enemies of the state" and a successful supply operation would have caused Stalin major political difficulty. He had no interest in dealing with the Poles as equals. They had airfields within a few minutes flying time which would have made our operation far more effective but these were expressly denied. Aircraft received ground fire from Soviet held territory; on balance it's unlikely Closterman's attack was a one-off accident.