First things first, McCullin is considered to be among the finest war photographers there ever have been. If there’s any doubt about that, you only need to look up on this link. More about his life can be found over here.
The most important thing about documentaries is how they show the reality and truth from whichever perspective they choose to, because documentaries don’t have the luxury of interpretations. They need to be true. McCullin himself talking about the various facets of his job as a photographer, as well as examplifying them by giving stories behind the pictures- while at each point not taking any sides takes care of the truth part. In all his life (and if you see picture, even you might appreciate why), he has tried to take pictures of the evils of war and how the power, greed or callousness on part of leaders creates such a scenario.
Talking about wars, and how he couldn’t take his first great picture because he couldn’t just fathom what had happened. He eventually got used to it from the side of soldiers and how they had to suffer- but held a humane approach and an underlying anti-war theme in majority of his pictures. The next phase comes when he covers some of those civil wars and how he witnesses moments of poise days before death, poverty, hunger, and so much more evils associated with war. He had his moments where he questioned his job, but kept on doing it.
In a gist, this documentary needs to be watched merely for the effects of war, and why due to the greed of a few a whole humanity dies so many times, why there’s no pride in winning a war because ultimately it’s the humans who lose. A must watch documentary.