"I was convinced we had done everything possible to keep this a war between warriors and not one of indiscriminately killing women and children," he said in an interview shortly before his death.
The most highly decorated Luftwaffe bomber pilot of the Second World War - a National Socialist to the end - has died in Germany few years ago.
He would not hear a bad word said about the government he served. An idol to young National Socialists, Herrmann flew in the first waves of attack on London that began on 7 September, 1940.
A veteran of warfare before the first bombers took off across the Channel - he served with the famous Condor Legion in the Spanish Civil War and in the campaigns in Poland and France - Herrmann was to become one of the Second World War's greatest pilots.
"My first sorties over England were attacking the Thames haven oil refineries and the Billingham nitrogen works," he said in an interview shortly before his death. "But especially hard was the raid on the Vickers-Armstrong factory in Newcastle-on-Tyne. I didn't think we would come back from that one, the flak was so heavy and the Spitfires and Hurricanes were chasing us all the way.
"And so, it came to my 69th combat mission of this war - the attack on London! My target was the India Docks in the east of London. I was convinced we had done everything possible to keep this a war between warriors and not one of indiscriminately killing women and children.
"But the indignation over the British war of terror on Germany swept our thoughts aside. We would fight like for like. I saw the bombs fall as the planes swooped over London and I saw the flashes as they exploded and the smoke rise high into the night sky. I knew that the Londoners would be down in their cellars and their underground stations as we released all of our bombs, all 100kg high explosive. As the bombs exploded I observed them with satisfaction."
Speaking of his enemy, he added: "I came to respect their hardness and bravery, cunning and trickery, and also their occasional doziness and weaknesses, which I put down to their habit of having tea-breaks every day".
The last mission against Britain was flown in November when his Junker squadron was ordered to the Mediterranean.
In February 1941 his group went to Sicily, where they flew against Malta and Greece. In one such attack, he dropped a single bomb on an ammunition ship.The resulting explosion sank 11 ships and made the Greek port of Piraeus unusable for months.
July 1942 saw him assigned to the general staff in Germany, where he became a confidant of Herman Goering.
Later he created the famous Wild Boar night-fighter squadron that took a devastating toll on British bombers over Germany.
By 1944 he was inspector general of night fighters and received the Oak Leaves and Swords additions to his Knight's Cross from Hitler. So fanatical was he in defence of National Socialism that he led the so-called Ram-hunter squadron, which consisted of young pilots who were supposed to ram Allied bombers in a kamikaze-like rearguard action.
After the war, he was imprisoned in a gulag by the Russians for ten years, and on release became a Dusseldorf-based lawyer defending National Socialists as well as Holocaust revisionists, including the British historian, David Irving.