The British military confronted significant challenges during the invasion of Iraq and Afghanistan. Adhering to the principles and doctrines of previous campaigns, they failed to prevent Basra and Helmand from descending into lawlessness, criminality, and violence. By juxtaposing the deterioration of these cities against Britain’s celebrated legacy of counterinsurgency, this investigation identifies both the contributions and limitations of traditional tactics in such settings, exposing the gap between the ambitions and resources, intent and commitment, that proved so disastrous to the operation. In its detailed account of the Basra and Helmand campaigns, this volume conducts an unprecedented assessment of British military institutional adaptation in response to operations gone awry. It calls attention to the effectiveness of insurgent tactics and the danger of ungoverned spaces shielding hostile groups and underscores the need for the British military to acquire new skills for meeting irregular threats in future wars.