I used to do that job for Reuters, while I didn’t do Africa, I did cover a lot of the Texas death penalty cases in the late 1990s as well as various natural disasters. It’s a tough business. But you have to be detached enough or the world never knows the truth. My good friend Adrees Latif (multiple Pulitzer winner,) covered the violence in Myanmar, the migrant caravans and a bunch of other tough stories and it can definitely take its toll, but it’s a vital profession. One photo can change the world as Eddie Adams proved in Vietnam.
“Max Hastings, writing in 2018, noted that Lém was in civilian clothes and was alleged to have just cut the throats of South Vietnamese Lt Col Nguyen Tuan, his wife, their six children and the officer’s 80-year-old mother.[7]
According to Article 4 of the Third Geneva Convention of 1949, irregular forces are entitled to prisoner of war status provided that they are commanded by a person responsible for his subordinates, have a fixed distinctive sign recognizable at a distance, carry arms openly, and conduct their operations in accordance with the laws and customs of war. If they do not meet all of these, they may be considered francs-tireurs (in the original sense of "illegal combatant") and punished as criminals in a military jurisdiction, which may include summary execution”
So by the circumstances, the execution was likely completely justified and in keeping with the Geneva Convention, but the photo did not present that context. As such, it served as North Vietnamese propaganda and undermined the entire US war effort.
Was "breaking the Geneva conventions or not" an aspect of that photo the public primarily cared about it?
How is undermind the US war effort in Vietnam a bad thing in and of itself? That war and the justifications for it undermined the US in a way that still keeps giving. The protest sparked good things and bad things -- the rationalizaton of the war produced only extremely bad things, fit to kill a persons soul and intellect, with god knows what half-life. I didn't downvote you, but I disagree.
It's a great example of how to be factually correct while completely missing the point. Saying "well, his summary execution was completely legal" is a bland form of words. The photo shows us what that looks like, and how intuitively horrifying it is. A million deaths is a statistic (or in the case of Vietnam per wikipedia, 1,353,000). An individual death is a tragedy - and here is a photo of that.
The casualness and lack of ceremony of the execution is a key part of the impact of the photo. Was means the casual extinction of huge numbers of lives. Modern war means this happens at a distance and is comprehended statistically. "Another few hundred people were fed to the meat grinder today." Photographing it reconnects people to the dead as humans.
As for "undermining the war", America's role in Vietnam was always on a really shaky moral footing since it was essentially colonialist; it was always right to question this and "undermine" it.