Portraiture originally started as photography, where the artist was always in control s they could make someone look exactly how they wanted to be portrayed.
With the birth of photography portraiture, majorly, switched over to being done with cameras as this was quicker to do and did not require a subject to sit around for hours on end holding a steady pose.
However, photography being such a new method it still placed its customers at the mercy of the photographer.
In times of war a photographer stands a chance to make his most compelling shots, they can change wars and they can also create them. Some examples are Eddie Adams', not really a portrait in the more used meaning of the word, but still it was an image that portrayed how this character acted with the execution of a Vietnamese soldier. This made America feel they should withdraw from Vietnam as they did not want to support these soldiers. In a case of starting a war, there was the image someone drew of Allah in a newspaper which sparked all kinds of anger and aggression, this was not really a portrait but still depicted someones view.
All portraiture really is, in my opinion, is where a photographer sets up an image to portray a person in a way that they see as suitable. Portrait images generally come across to me as being fake. This statement stands more towards photos that have been taken in my life time. Before my lifetime I would generally say that portraits were portrayed in a more real fashion.
Now, in portraits, you have people with fake smiles while they worry about everything else, although in an earlier statement I made, you can still tell if someone is faking a smile to someone who really is. This can still mean that the photo is really putting across the real feeling. (ROUGH)