His painting of Prince August of Prussia (a son of Prince Augustus Ferdinand of Prussia) and Count Neidhardt von Gneisenau laid the foundations for his fame as a portraitist and also led to further depictions of the royal family.
Henry Peter Bosse claimed to be the grandson of Count August Neidhardt von Gneisenau.
In 1943 Caspar was engaged by the director Veit Harlan to play the young August Neidhardt von Gneisenau, who in 1807 defended the Prussian fortress town of Kolberg against the French during the Napoleonic Wars, in Kolberg, an epic film produced on the orders of Goebbels.
Johann Wolfgang von Goethe | Otto von Bismarck | August Strindberg | Alexander von Humboldt | Wernher von Braun | Carl Maria von Weber | Herbert von Karajan | August | Gebhard Leberecht von Blücher | John von Neumann | Lars von Trier | Ferdinand von Mueller | Paul von Hindenburg | Alexander von Humboldt Foundation | Heinrich von Kleist | Anne Sofie von Otter | Erich von Stroheim | Papal conclave, August 1978 | Max von Sydow | Justus von Liebig | German battleship Gneisenau | Stanisław August Poniatowski | Hermann von Helmholtz | Franz von Papen | Die Meistersinger von Nürnberg | Carl von Clausewitz | Von Ryan's Express | Richard von Weizsäcker | August Derleth | Theodore von Kármán |
Dyhern's grandniece, Baroness Caroline de Kottwitz, was the wife of the famous Prussian field marshal Count August Neidhardt von Gneisenau, who was a prominent figure in the War of Liberation and played an important role in the Battle of Waterloo under Blücher in 1815.