Abstract: A recurrent theme in command and control (C2) concerns the most appropriate size of deployed HQs. Opinions vary, and the subject is clouded by the impending impact of digital battle management systems. However, the question is not directly related to digitization. HQs in the World War II were considerably smaller than at present. Their subsequent growth is attributed to the increasing complexity of modern war. But how much more complex is modern war? Is the attendant increase in HQ size justified? Indeed, how should one justify the size of an HQ? This paper discusses the role of an HQ in supporting command and control and suggests six linked premises: that the quantity of information used to make battlefield decisions is very small; that operation orders should be, can be, and have been very short; that very few staff are required to produce those orders; that there is significant advantage in making and disseminating decisions much faster than at present; that decisions do not have to be as good if they are produced significantly faster; and that there are significant advantages in deploying smaller HQs. These premises are considered using historical examples, apparent inconsistencies within doctrine and practice, and two novel models (of decision-making and organisational complexity). The paper then proposes a hypothesis that formations and units with small, closely integrated staffs can be significantly more effective than those with HQs of current dimensions. Discussion of the emergent hypothesis suggests a re-evaluation of the apparent complexity of modern war; of the nature of operational control; of decision-making methods; and of the impending effects of digitization. Future concepts for C2 organisations require further consideration, and perhaps experiment.