Some of the hottest temperatures ever experienced in a city fire accompanied the hurricane-force winds. The sheer amount of flammable material, stacked up in six-storey buildings, like huge charcoal ricks, produced enough heat to melt the glass in the windows of cars and trams on the streets – which means the temperature must have approached glass-furnace level, about 1,400°C. 6Inside the buildings it was even hotter – cutlery and glass bottles melted, and bricks burned to ash.
In the years that followed the catastrophe, the Hamburg fire-storm came under intense scientific scrutiny, and it was concluded that no other large fire in recorded history has ever equalled its intensity. It was far worse than any of the great forest fires that have engulfed large parts of America and Canada; greater even than the fires that have consumed London, Chicago or any other city bombed by the Allies across Germany.
The reason Hamburg’s firestorm was so bad is as simple as the result was tragic: weather conditions – a set of circumstances so unusual for the area that they have only rarely been repeated since. Because of all the hot, sultry weather Hamburg had been experiencing, an unstable pocket of warm air was sitting directly over the city. It had been warmed by all the fires that had been burning since Sunday, and was saturated with smoke particles, which retained the heat even more effectively. All around Hamburg, however, and high above it, the air was much cooler. Surrounded on all sides by this colder air, the pocket of warm air was like a huge, pressurized balloon, sticking up some 10,000 feet. All it would take to burst the top off this balloon was a sharp rise in temperature. Once it hadburst, the warm air over the city would rise unrestricted for thousands of feet, rapidly drawing newer air behind it, and setting off the greatest firestorm the world has ever seen. 7
The final factor was the humidity – or, rather, the lack of it. Because the city is close to the sea, the air in Hamburg normally has a very high humidity – a seasonal average of about 78 per cent. On 27 July 1943 the humidity was a mere 30 per cent. After the long, dry summer most of the buildings in Hamburg were like tinder, but with such low humidity there was nothing to stop the rapid spread of fire. Other historians have used the analogy of a furnace with a very tall chimney, just waiting for someone to light a match. 8That match was lit shortly before 1.00 a.m. when the RAF dropped the first of 1,174 tons of incendiaries into the eastern quarter of the city.
* * *
Part of the tragedy for Hamburg was the sheer bad luck of it all. The Allies had not planned specifically to take advantage of the prevailing weather conditions; indeed, they did not even realize that such conditions couldlead to a firestorm. 9Their understanding was far more basic: the weather was good because it was clear, which made navigation to the city much easier, and because it was dry, which would make it easier to start effective fires. They had no idea quite how perfect the conditions were for their purpose.
They did, however, have a good idea of how to start fires, and how to keep them going. After years of practice, they had created a highly effective system. To start with, they knew that the most important factor was concentration. If an attacking force dropped its incendiaries in a single area it would be impossible for the defenders to put out all of the fires. If enough were allowed to take hold, they would soon join up into huge conflagrations. The fire services would be unable to cope: they would be forced further and further away from each fire’s centre, and would struggle to prevent them spreading to other districts.
The second most important thing was the use of high-explosive bombs. Most people assume, instinctively, that the purpose of explosives is to destroy buildings. Our perception is coloured by our modern experience: the bombs used by terrorists, or even by conventional military forces, are almost always designed to cause maximum damage to buildings by razing them to the ground. But bombing during the Second World War was carried out on such a huge scale that different tactics were required. Fire is far more efficient than high-explosive bombs at destroying large areas, so Allied tactics were aimed at getting the fires to spread as far and as quickly as possible. Military planners had learned early in the war that if they wanted their fires to spread it was counter-productive to blast buildings down because this created fire breaks. The purpose of high explosives, therefore, was not to destroybuildings but merely to blow in as many doors and windows as possible, to allow the air to get inside and feed the flames. Buildings that were not yet burning would catch fire as the sparks and embers from neighbouring buildings floated in, setting curtains and furniture alight. By blowing off roofs, high-explosive bombs would also allow the incendiaries to pierce the lower floors of a building, where they could do most damage. The explosions would have the added effect of keeping most fire-fighters inside their shelters long enough for the fires to take hold, and putting craters in the roads that prevented fire engines getting to affected areas. So while the incendiaries would do most damage, high explosives had an essential role, and it was important that the exact mix of the two different types of bombs was right. 10
One might be tempted to ask what kind of mind comes up with such theories, but to be fair to the Allies a great deal of the research had been done for them – or, rather, tothem. During the Blitz in 1940–41, the Luftwaffe had rained incendiaries on London and other cities, causing huge damage. The British, who had only really used high-explosive bombs until then, soon learned that the fires did far more damage than the explosions, and began to experiment accordingly. 11Repugnant as it might seem now, the cruel logic of war requires such efficiency. By the summer of 1943, RAF planners had brought large-scale bombing to a fine art.
* * *
The concentration of bombs on Hamburg that Tuesday night was so great that the civil-defence organizations in the eastern quarter of the city had little chance of saving anything. ‘After only a quarter of an hour, conditions in these districts were terrible,’ claimed the official German report shortly afterwards. ‘A carpet of bombs of unimaginable density caused almost complete destruction of these districts in a very short time. Extensive portions were transformed in barely half an hour into one sea of flame.’ 12The bombs came down so thick and fast it was impossible to stop the spread of fire: tens of thousands of individual fires quickly became one vast conflagration.
The people of Hamburg had been expecting another attack, but nothing could have prepared them for the hammering they were now experiencing, especially in the eastern quarter of the city. Even those who had lived through the first night of attacks must have been shocked at the intensity of tonight’s bombardment. For Fredy Borck, the eleven-year-old who lived in the riverside district of Rothenburgsort, it was the most terrifying night of his life:
Suddenly it started to happen outside. It was a bombardment that is still indescribable, even today… All around us were the crashes of bombs striking with appalling explosions – ear-shattering explosions that seemed to be right next to us, over us. You could even hear the howl of the nearer bombs before they hit, then the crash as they burst. It must have been hell outside! It got worse and worse. The walls of the cellar rose and sank… An inhuman screeching and groaning came from the walls. We screamed along with it, screaming out our terror! We lost all self-control, crouched on the benches, cowering together with our heads between our knees to cover our ears. 13