Returning to his homeland, he participated in the Committee on Vietnam of the German Democratic Republic and in activities promoting the solidarity with Vietnam.
After retiring, he spent time on collecting documents and writing books on Vietnam, including a book with Vietnamese version entitled “Ho Chi Minh – Mot bien nien su” (Ho Chi Minh – A chronicle), “Berlin – Bonn – Saigon – Hanoi”, “Vietnam - ein dreizigjähriger Krieg 1945-1975” (Vietnam – A 30-year war 1945-1975), and “Duong mon Ho Chi Minh” (Ho Chi Minh Trail).
In 2012, Kapfenberger handed over to Vietnam a Ho Chi Minh Order of the German Democratic Republic, which was the only country that had an order named after Ho Chi Minh, and some other items illustrating the solidarity with Vietnam.
At the presentation ceremony in Berlin on December 15, Vietnamese Ambassador to Germany Doan Xuan Hung appreciated Kapfenberger’s contributions to the two countries’ relations.
The diplomat also briefed participants about bilateral ties and cooperation prospects while voicing his hope that Kapfenberger will continue supporting this relationship.