He was aware of Karl Fairburne's activities in attempting to disrupt his activities. He is fairly calm when he comes face to face with Karl in the Ratte production factory, expressing respect for Karl's skill as a sniper, though Karl only views him with disgust. He states that he and Karl are not so different, and idea which Karl claims is not true.
After destroying the Ratte, Vahlen is trapped under debris and pleads for Karl to free him. Karl takes Vahlen's Luger, and says that the difference between them is that he remember's everyone he kills, before executing the General at point blank Range.
Unlike other antagonists/targets, Vahlen is not directly killed by the player, though the player does trigger the explosion with causes him to be buried under debris before being killed by Karl in the final cutscene.
Vahlen's epaulettes are those of a Field Marshal.