Here’s a thought. Why don’t we legislate for a statutory, independent inquiry after every war (except, perhaps, those started by others)? The inquiry should be given certain inviolable powers in advance – the right, for instance, to examine relevant intelligence and to require senior figures to testify – to prevent Governments from limiting the range of any post-war inquiry (as Thatcher’s Government did with the neutered Franks Report into the Falklands War in 1983).
The inevitability of such a formal inquiry (and the following, also compulsory, Parliamentary debate) might just contain Governments’ over-enthusiastic war-making and provide more interesting material for historians than we’re used to.