years in the humanities and social sciences [@WF94; @CSW2005].

Recent advances in the theory of networks have provided us with the mathematical and computational tools to understand such phenomena better. One striking result is that a network much of whose connectivity comes from a small number of highly-connected nodes can be very efficient, but at the cost of extreme vulnerability. As a simple example, if everyone in the county communicates using one telephone exchange, and that burns down, then everyone is isolated.

This paper starts to explore the tactical and strategic options open to combatants in such conflicts. What strategies can one adopt, when building a network, to provide good trade-offs between efficiency and resilience? We are particularly interested in complex networks, involving thousands or millions of nodes, which are so complicated (or under such dispersed control) that the resilience rules can only be implemented locally, rather than by a central planner who deliberately designs a network with multiple redundant backbones.

Is it possible, for example, to create a virtual high-degree node, by combining a number of nodes which appear on external inspection to have lower degree? For example, a number of individuals might join together in a ring, and 