Photographer Don McCullen focuses on Vietnam in his latest book | Don McCullen

After more than seven decades of covering conflicts around the world, Don McCullen will return to Vietnam and its most famous photographs in his latest book.

The photographer, who started his career at the age of 23 when his photo of a gang in Finsbury Park was published in the Observer, decided to revisit the war and his 12-day mission with the US Marines during the Battle of Hue in 1968.

McCullin’s photographs of the battle, which include a traumatized American soldier, are among the most iconic of the conflict and are widely credited with helping to turn public opinion in the United States against the war.

McCullin said he was still haunted by some of the photos he took during one of the bloodiest and most notorious battles of the Tet Offensive, which he described as “absolute madness and insanity.”

“They harass me at night when I go to sleep,” he said. “They came back to me uninvited, and then I started saying, ‘Could I have done better? Could I have done this or that?” “The actual battle I fought, and the last big battle I fought in 1968. I saw a huge number of American soldiers being killed near me.”

One of his editors at The Sunday Times was Harold Evans, who said McCullin’s secret ingredient was empathy for his subject – whether it was criminals in north London or guerrilla fighters in central Africa. He combined his “cold eye with the warmth of his compassion,” according to Evans.

Before being sent to Vietnam, McCullin had begun his career shooting conflicts in the Congo during the bloody and chaotic run-up to independence, and in Cyprus, where he covered the civil war between Turkish and Greek factions. He was also present during the building of the Berlin Wall and the erection of the Iron Curtain across Europe.

He retired from war photography at the age of 75, when he visited Aleppo in Syria and was no longer mobile enough to quickly get out of harm’s way if necessary. Since then, he has published books on his other interests, including ancient Rome.

So why does he return to that war for his latest book, called Vietnam? Why not revisit his work in Belfast or Biafra? “Because of all the wars that have been fought over the last 20, 30, 40 years, there has never been a war like Vietnam,” he said. “Unfortunately, 58,000 American soldiers were killed and 300,000 were wounded. It was an extraordinary American adventure.”

McCullin made 16 trips to Vietnam. His new book includes 100 photographs and war equipment, including his helmet with the words “Times England” emblazoned on the side and his muddy compass.

McCullen, now 91, is arguably the most famous British photographer alive. He has mounted a retrospective exhibition at Tate Britain, touring shows of his work have spread around the world and he continues to work from his base in Somerset.

While his photographs have often brought the horrors of war into wider public attention and in many cases have helped build a moral case for ending conflicts, he is not convinced of the power of his photographs to bring about change.

“I made no impact at all,” he said. “I came out with these pictures and they were published and people were shocked to see them. But look at the wars that have happened since Vietnam. They’ve all been bad luck, too. I’ve been in many wars in Lebanon, and they’re still going. How can I make a difference, really?”

The book will be released in October via Gost Books.