Hahnemann played 23 games from 1935 to 1948 for the
Austria national football team and scored four goals in these appearances. After the
Anschluss that united Austria and Germany, Hahnemann played 23 matches for
Germany's national team between 1938 and 1941, scoring 16 goals. He also appeared with the German squad that took part in the
1938 World Cup in
France. In a 1940 international match he managed the feat of a double hat-trick in a 13:0 victory over
Finland. The only player to score more goals for Germany in a single match was
Gottfried Fuchs who scored 10 times against Russia at the 1912 Olympic games in Stockholm. He also played for Austria at the
1948 Summer Olympics. After his playing career, he became a manager with
SpVgg Greuther Fürth and in Switzerland. ==Honours==