Brian Donlevy received his only Oscar nomination for portraying Sergeant Markoff in Beau Geste.
Brian Donlevy shows up when the brothers are in the French Foreign Legion, and it is pretty clear exactly who Sergeant Markoff is going to be from the outset. Sergeant Markoff is evil, cruel, and sadistic. He is part of the legion only for his own sick satisfaction as well, as his own personal gain. Donlevy never tries to hide this fact in his performance, and he plays him as completely evil from beginning to end.
Donlevy never tries to act in any other fashion otherwise than the pure bad man heavy fashion. He talks loudly with cruel voice, and always trying to be domineering over the men he mistreats. Donlevy performance really is rather simple and one dimensional, but that really is the character of Markoff. And as that one dimensional evil villain character, Donlevy really is not half bad.
There is not much subtly in this performance that is for sure, but Donlevy does convey the cruelty and sadistic tendencies of Markoff as they should be. This is not an amazing villainous performance by any measure, but Donlevy still is appropriately effective in being evil, you certianly want him to get his comeuppance and his evil is realized well enough. This is not a great performance, but certainly does serve its purpose to the film.