Hurricane Katrina this morning claimed its first political scalp with the resignation of Michael Brown as head of the Federal Emergency Management Agency. But, two weeks after the event, what lessons have been learnt so far?

First, a death toll of even hundreds represents a major human tragedy and causes huge dislocation. We should look back with renewed horror at the Cold War strategists who told us we should be prepared to fight a limited nuclear war – which at best would have yielded a thousand times as many casualties.

Second, exploiting tragedy for political ends is a game two can play. The Bush administration has taught Americans that nothing is beyond the range of party politics, that every disaster can be used for partisan purposes. Sure enough, the Democrats have taken note, and are now exploiting Hurricane Katrina just as shamelessly as Bush exploited 9/11.

Third, the bureaucratic response to September 11 – the creation of a monster new government department, Homeland Security – was a really silly idea. In 1949, 160 years after its creation, the US government still had only eight departments, but the last 56 years have added another seven. It’s hard to see anywhere that that’s improved things.

Fourth, the left’s notion of moral equivalence between terrorist attacks and natural disasters is nonsense. It’s perfectly coherent to say that government has a duty to protect against one but not the other (because one involves marshalling force against others, perhaps a dangerous thing to leave in private hands – read some social contract theory). But that’s no real use to the Bush people; saying you shouldn’t have taken on a responsibility in the first place is no excuse for screwing it up once you have taken it on.

Fifth, the Gone With the Wind-style idea that the south is a cultivated and genteel repository of American virtues is a myth; under the thin veneer of civility it has always been a brutal and dangerous place. In terms of civilian response to disaster, godless materialistic New York did much better and showed much more genuine solidarity.

Sixth, civilisation is a fragile thing; the descent into barbarism is easier than we like to think. With hindsight, the biggest contribution the Iraq war made to the disaster may be not that it depleted the reserves of National Guard, but that it depleted the respect for the rule of law and endorsed the message that might makes right. And the ultimate carrier of that message is a looter with a shotgun.