The Apollo Pact was an agreement between
Germany and
Communist Russia between the end of
World War I and the rise of
Adolf Hitler and the
Nazi party. It allowed Germany bypass military conditions in the
Versailles Treaty by training German troops in Communist Russia. These soldiers were mostly airmen and tank crewmen, since Germany was forbidden from having an airforce and tanks due to conditions in the Versailles Treaty.
The Apollo Pact was created out of the sense that the Germans and Russians had common enemies in the United States of America and Great Britain. Since the US had much of South America and the Pacific under its thumb while Great Britain controlled much of Africa, the Middle East, and India, they controlled many of the oil-producing areas and trade routes that the Germans and Russians depended on.
The irony of this pact is that many of the Germans trained during this time would be serving as senior officers during Germany's ill-fated offensive against the Russians. It is likely that many of the tactics and terrain studies were used in their drive towards Moscow.