The books describes for the first time, aerial combats between Swiss fighters and German combat aircraft. The fights in May and June 1940 resulted in a total of eleven losses of German aircraft vs. three losses on the Swiss side.

The German government was not happy with the result of these incidents and intended to punish Switzerland by requesting to return the recently bought Me 109 aircraft and many other things.

The author himself was a witness of these events during his time as aerial observer with the Swiss Army. He later became commanding officer of the Swiss Air Force.