How do militaries improve operational performance in war? Improve- ments may involve major organisational change. But, equally, they may involve only minor change to how militaries operate, or indeed no change at all (just better implementation of existing organisational routines). Up to now the scholarly literature has focused on the imperatives and pro- cesses of major military change, i.e. military innovation.2 But innovation is neither a necessary nor a sufficient condition for victory in war. What victory almost certainly requires is for militaries to adapt to the operational environment and challenges they face, both when they first deploy and as the campaign evolves. This chapter develops a theory of military adapta- tion, which it applies to an analysis of the British campaign in Helmand from 2006-2009. It shows how British brigades adapted different ways of using combat power to try and defeat the Taliban from 2006-2007, and how from late 2007, British brigades have adapted a new population- centric approach that has focused more on influence operations and non- kinetic activities.