This is another image which has become immortal. While the majority of US military interventions around the world have gone well for the country, Vietnam didn't. It failed spectacularly, and the Americans had to retreat after being humiliated.
If anything could sum up the Vietnam experience for the soldiers who fought there, it's this picture; a young man with piercing eyes, staring at the lens almost accusingly with 'war is Hell' written on his helmet. In many ways, he spoke for his generation without saying a word.