It seems there is increasing talk in America about building high in defiance of terrorist attacks. In the early days after 11 September it was low-rise, ground-level, underground and dispersal that were the favoured solutions. Now, resurgent Yankee confidence is saying that it is not beyond the wit of American architecture and engineering to make defensible skyscrapers, even whole cities of them.
What American cities need now, goes the current thinking, is proper defences.
So might the cities of America resume their old character as frontier outposts, their towers bristling with anti-aircraft guns instead of stockades and cannon? Not likely, but there is a lot of history regarding the fortifying of cities and not all of it is fictional.
Take HGWells, for instance. He visualised the use of atomic bombs against New York, dropped by a fleet of German airships, in the novel The War of the Worlds, published as early as 1904. And not much more than 10 years later, the Imperial German Navy really was planning to send airships across the Atlantic to bomb New York. Indeed, it was only prevented from doing so by the loss of the commander of the projected raid in a preliminary mission off the British coast.
Years later, when the US entered the Second World War against Germany and Japan, the prospect of bombing New York arose again. But while the Japanese succeeded in sending robot incendiary balloons across the Pacific in an attempt to start forest fires on the American west coast, the Germans were never able to launch V2 rockets from submarines against New York, which they had intended to do. Instead, they had to be content with lobbing a few shells into Atlantic City from a U-boat, without noticeable effect.
Still the US military took the danger seriously.
They feared German air raids - on New York in particular - because they had studies made of the kind of damage and casualties that might be inflicted by bombs striking skyscrapers at acute angles, and were thoroughly alarmed at the results. So much so that they remained alert to the possibility right up until the end of the war.
So, too, did Adolf Hitler, who had also had studies made with pictures of New York in flames. Although the Germans only had one four-engined bombing aircraft that was capable of flying to New York and back from mainland Europe, the Messerschmidt 264, there were rumours that smaller jet-bombers might be launched from U-boats on one-way missions. These rumours spread panic when the last German submarine wolf pack was dispatched to the US eastern seaboard in April 1945. Nor, for that matter, did the fear of a possible German atomic bomb entirely disappear until the country was defeated and occupied.
After the end of the war, there was a mass of evidence to support or reject the defensibility of fortified cities. The French Maginot Line - a 320km strip of underground fortifications with a garrison as big as a small city came out best. It had deterred direct German attack in 1940 but the Germans had merely outflanked it instead. Its garrison of 300,000 men remained intact but, unfortunately, France itself surrendered.Cities on the surface had done rather worse. Vienna, protected by anti-aircraft towers looking somewhat like stumpy skyscrapers, had suffered little damage but major German cities such as Hamburg, Dresden and Berlin had been reduced to rubble. Worse still, cities that had been heavily fortified, such as Sebastopol in the Crimea, brought forth the worst in retribution. In 1943 the Germans levelled it with a monster 800mm railway gun.
Maybe armoured skyscrapers will not be such a good idea after all.