What was the cause for the ten-year civil war in Germany during Otto IV's reign?
Disputed king election
Power struggle with France
Conflict with the Pope
Invasion by England
Answer
The dispute of the king election was the main cause for the ten-year civil war in Germany during Otto IV's reign. The dispute started when Otto IV was elected king of Germany in 1209, but Philip of Swabia was also elected king by another faction of the nobility.
Unraveling the Reign: A Quiz on Otto IV, Holy Roman Emperor