On account of his 40th aerial victory claimed, he was awarded Knight's Cross of the Iron Cross with Oak Leaves. It was Germany's highest military decoration at the time of its presentation to Joppien. Fighting on the Eastern Front, he was killed in action with Soviet fighters on 25 August 1941.
As a result of his 40th aerial victory, he received the Knight's Cross of the Iron Cross with Oak Leaves, Germany's most respected military decoration at that time. Joppien was the recipient of this honor. He fought valiantly on the Eastern Front before being fatally wounded in combat against Soviet aircraft on August 25, 1941.