Professor Andreas Kessler is the secondary antagonist of Sniper Elite 4
Kessler was the head scientist of a new Nazi weapon. Later Major Hans Dorfmann (Heinz Böhm), reveals that Kessler is at the Maggazeno Facility where the missiles are assembled, Fairburne infiltrates the base to kidnap Kessler and steal his research notes. On interrogation, Kessler tells Angel her father is still alive, prompting the Partisans to depart to assault the town of Giovi Fiorini and find Böhm's confidant Major Klaus Rothbauer. Kessler then tells Fairburne that he is dying and is of no use to the Nazis or the Allies as a result, and that the information given to Angel was a lie in order to lure the Partisans into a trap.
After Böhm's death, and the invasion of main land Italy, Kessler was going to be "squeezed" for his knowledge by the Allies.
He seemed to be a friend of Dr. Wolff, as a letter sent by Wolff adressed to Kessler can be found in the game.