"There were two more kills scored by the leading ace which the Soviets credited, which Kozhedub was more than happy to forget. In April 1945, he saw an American B-17 being attacked by a pair of German fighters. Coming to the bomber's rescue, he fired a burst between the enemy machines and their intended prey, causing the Germans to break off their attack and dive away. Before Kozhedub could pursue them, he spotted an approaching formation of unfamiliar fighters. The leader of the group opened fire on Kozhedub at long range, and the Russian ace in turn pulled up sharply behind the last machine in the formation and shot it down in flames- the fighter fell among Soviet troops on the ground.
Pulling up in half loop, Kozhedub then fired another burst on the leader of the formation, who was also shot down. It was at this point that he saw the blue and white stars on the wings and fuselage of his "enemy". Kozhedub returned to the base extremely upset, certain that his actions would result in a major row with the allies. Fortunately, one of the American pilots managed to bail out, and when asked who shot him down, he replied "a Focke-Wulf with a red nose". Col. Chupikov gave Kozhedub the gun camera film confirming his two Mustang kills, along with the admonition, "Keep this to yourself - show no one"

taken from Mellinger's LaGG & Lavochkin aces of WW2 (p.83-84)

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For the first time I have seen "History" at close quarters,and I know that its actual process is very different from what is presented to Posterity. - WWI General Max Hoffman