Only those who experience firebombing by air fully understand the power of fire. For the rest of us, our understanding must come from the grisly details of numbers of lives lost and buildings destroyed.
The recent fire in Philadelphia that claimed two firefighters offers a small view into the scenes that British, German, and Japanese civilians and firefighters faced under sustained firebombing. Look at the dramatic photographs of the Philadelphia fire and imagine that large building fully involved in fire, but multiplied by hundreds or thousands of times in just one city, in one bombing raid.
In air raids, firefighting was grossly defensive and still many firefighters died.
The German cities of Dresden, with a population of 633,000, and Hamburg, with a population of 1.8 million, stand as examples of the destructive capability of fire as a weapon of war. They are better examples for this purpose than the Japanese cities of Nagasaki and Hiroshima.
The destructive potential of the atomic weapons used on those Japanese cities was in each single bomb's blast where the destructive wave of energy produced from the detonation emanated outward. The ensuing shock wave knocked down or obliterated everything standing in its path over a wide area and the release of heat energy incinerated what remained.
In contrast, firebombing with incendiaries and high explosives required a concentrated effort focused on specific targets in order to get numerous great fires and conflagrations going that in turn would extend and join to create one large firestorm. In 49 of Germany's principal cities, the firebombing destroyed 39 percent of all dwelling units.
The methods and tools of fire-raising
One air attack in particular, carried out by the Royal Air Force on Hamburg in 1943, created the largest and most destructive urban fire known up to that time. Without question, the atomic bombs dropped on Japan created damage on a much greater scale eclipsing the destruction of Hamburg and Dresden.
However, the firestorms created by the bombing of German cities should interest us as firefighters from the aspect of fire protection and operational fire defense.
The weapons of choice were incendiary and high explosive bombs, the former to start fires and the latter to spread fire and keep firefighters away.
The four-pound magnesium incendiary used a thermite igniter with a two-pound iron weight to facilitate the bomb penetrating through wood roofs and floors. The four-pounders were extremely effective when dropped in mass over specific fire cells with the expectation of creating a large fire within an area bounded by parapeted firewalls.
The drawback to the four-pounders was their inability to penetrate deep enough into four- and five-story buildings. To achieve greater penetration they used a 30-pound oil bomb.
This incendiary contained benzole (or benzene, a natural constituent of crude oil and an aromatic hydrocarbon) plus white phosphorous. Bomb loads carried by RAF aircraft included four- and 30-pound incendiaries combined on a 50-50 basis by weight. The heavier incendiary penetrated deep into structures and burned with a blowtorch effect.
Ton for ton, incendiaries were 4.8 times more effective than high-explosive bombs dropped on homes, apartments, mercantile business and small industrial shops. Seventy percent to 80 percent of damage was due to fire rather than explosions, especially where great fires and conflagrations massed to form firestorms.
When fire and weapons experts surveyed the burned cities, they determined that concentrated area bombing created firestorms in Hamburg, Kassel, Darmstadt, and Dresden. The firestorms in these four cities differed from the peacetime conflagrations that burned in Chicago and other American cities in the late 1800s.
Numerous block fires and larger great fires extended rapidly, merging into one great mass of fire blanketing a wide area, whereas conflagrations typically begin from one point and grow in size.
The post-fire survey of Hamburg concluded that within 20 minutes two out of three buildings over a 4.5-square-mile area were heavily involved in fire due to incendiary bombing. The intensity of the fire was so great as to keep fire defense forces from leaving their fire stations.
Examination of wooden window frames, shutters, and doors of buildings in the target area revealed that fires burned downward through the floors of each building individually with virtually no spread building to building. The fire venting through the top of each building and the sheer number of structures set afire supported creation of a firestorm over a wide area with a large and powerful thermal column.
In Hamburg, the thermal column was estimated at 2.5 miles high and 1.5 miles in diameter. At 1.5 miles from the column's center, winds of 11 mph to 33 mph pulled fresh air back into the fire's center to feed necessary oxygen for combustion.
The winds uprooted trees with three-foot diameter trunks and hampered firefighting operations, making it difficult for firefighters to deploy and disrupted hose streams. Because fire stations were targets for the bombers, the firefighters often deployed to inconspicuous locations with fire apparatus until it was less dangerous to venture out.
Firefighting was defensive in nature and only possible at the perimeter of the block fires and great fires, here they could stop the spread but not extinguish fires in individual structures.
Defensive firefighting and rescue
Giving up actual firefighting efforts in many instances, Hamburg firefighters turned their attention to assisting people escaping from the basements of burning buildings where they had sought protection. The heroic effort saved 18,000, however 55,000 died in the basements of Hamburg.
Those who died did not burn; rather they suffocated as the hungry fire above and around them consumed all available oxygen. The fire incinerated those who did attempt escape from the basements into the streets. In the Hamburg raid, the toll was as follows:
- Of the 55,000 dead, only 45,000 bodies were recovered
- 37,500 dwelling units were destroyed and 4,660 severely damaged
- Of 450,800 family apartments, 253,400 were destroyed
- 5.9 square miles of buildings were destroyed
The design of city water systems in European countries, on a per capita basis, supplied only 35 gallons per minute per capita per day. In contrast, Chicago's water system supplied 350 GPM per capita per day.
The water systems in the firebombed cities presented a challenge to firefighters from a supply standpoint as the bombs were constantly destroying the supply mains. Firefighters had to establish hose relays, sometimes over 6,000 feet. The British and German fire forces both developed capabilities to construct temporary water mains laid out above ground.
With pumpers typically rated at 660 GPM, they experienced difficulties supplying long relays under draft from static sources. In addition, they lacked large-caliber monitor and turret nozzles for attacking large fires.
They used handlines of 2-inch or 2 3/4–inch diameter, single-jacket hose with or without a rubber lining. The single-jacketed hose lacked the strength to stand up to the rough demands of wartime firefighting.
Despite questions on the morality of the Allied forces firebombing, the devastation helped disrupt the German war effort and hindered the Germans' ability to endure ever-greater hardships for the sake of Hitler's war.
After the war, the NFPA engineers involved in the British firebombing research effort strongly urged that future city and town planning in America follow an open-space pattern to provide natural firebreaks in built-up areas. They offered up the traditional New England zoning rule of minimum one-acre lot sizes as the ideal target.
In the post-war years of suburban growth, planners and developers followed that pattern. It ultimately contributed to suburban sprawl and in some cases impingement of growth into the wildland-urban interface.