On 15 October 1942, he was incorporated to the Wehrmacht and become one of the "malgré-nous" (despite ourselves), young men born in Alsace or Lorraine enrolled against their will into the German army who had to fight with their enemies against the people they supported. During the next three years, he criss-crossed Europe without much recollections of events, places and dates. This time he was sent to Yugoslavia. While fighting the local resistance, he and his fellow soldiers burned isolated villages inhabited by women and children only. One day he found himself in front of a partisan who broke Seel's jaw, as a result of which he soon lost all his teeth. The man did not recover from the ensuing fight. Wounded, Seel was sent to Berlin in an administrative position.