Germany, beaten by Australia in the final in 2010 at New Delhi, were winners of successive World Cup titles in 2002 and 2006.
South Africa kept the German strikers at bay until they conceded a penalty stroke in the 27th minute that was converted by Christopher Zeller.
Thilo Stralkowski increased the lead just seconds before half-time with a strike in the open play.
The South African goal fell twice in the space of four minutes in the second session with Mats Grambusch (56th minute) and Oliver Korn (59th) firing on target to launch the German campaign with pull points in the first Group B outing.