Background history on the photo
The reason why this photo was so famous is because it showed the disapprove and fierceness of our war leader, the story behind this is what will ultimately make it famous.
Churchill was brought into the speaker's chamber to have his photograph taken, where he had the studio set up.
The story was winston churchill didn't want to have his photograph taken because he was in a bad mood, so he pulled out a cigar and started to smoke on it. Yorsuf karsh went up to him and said "forgive me sir" then he took the cigar out of his mouth and winston churchill became very upset and that is when the photograph was taken
I think the backstory and how the scowl on his face is all very real as the photographer grabbed the cigar out of churchill's mouth then took the photograph.
To improve the photo the only thing I would do would slightly brighten the face to make it a bit more of a focal point, because as gray as it is, it blends in with the rest of the photo.
I think this photo captures the personality of Churchill perfectly, the photo was not taken as a pose but as a reaction of the photographer taking the cigar away from Winston Churchill.