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.
Due to his 40th aerial triumph, he was honored with Knight's Cross of the Iron Cross with Oak Leaves. At that time, it was Germany's most prestigious military honor bestowed upon Joppien. Engaging in combat on the Eastern Front, he met his demise in action against Soviet pilots on August 25, 1941.