General David Petraeus advises Americans and their allies to be coldly realistic about what force can achieve. Oddly, he also advises them to prepare for a future where small wars are pretty much inevitable, where America must intervene early to prevent worse things happening later on, and where ‘stabilisation’ is a core part of war itself. Because, ultimately we sometimes have no choice. Looking back on the ‘lessons’ that have been ‘written in...

