Network based defence (NBD) creates new possibilities for the Armed Forces to conduct electronic warfare operations (EW). In addition new types of vulnerabilities and threats emerge towards the "network" as well as to single platforms, command and control structures and the information systems. In order to reduce the vulnerabilities within NBD, it is necessary to implement studies on a system of system level. The aim of the report is to describe and discuss in general terms how the transformation into a network based defence may influence EW and how NBD will be affected by EW. An overall goal with future EW against network centric structures, is to put pressure on the adversary´s most vital nodes and links; e.g. his centres of gravity (CoG). Each network has, independent of if they are hierarchical, centralised, decentralised or distributed, their own vulnerabilities and strengths built-in due to their network structure. If you understand your own structure as well as your opponent´s you can find the CoG´s to influence with different EW means and methods. The most robust structures are the decentralised as well as the distributed ones. If you obtain knowledge of the CoG´s in a network it also gives you a possibility to protect your own systems. A conclusion is that a fruitful methodology for EW on a strategic and operative level should use theories based on centres of gravity as well as the logic of networks. The technical developments towards smaller, cheaper and more effective components give new possibilities to distribute EW capacity from EW battalions to other units. The transformation requires a good coordination capability between the units. A consequence of an elongated distribution may be a need for development of new battle techniques and procedures.