The author collected the files from the archives of the Russian Federation, from the Bundesarchiv, and from other nations participating in the war. After collecting the files, he proceeded to translate them, check them, and perform a data verification.

If both sides agree on the data, a single common figure is shown. If the data does not match, then German and Soviet data are shown.

The author tried to indicate the data as accurately as possible, but he had not the opportunity to be on the front line so he cannot conjecture about figures, as it would go against his credibility, so he exposes all the data and the readers must draw their own conclusions about it.