This report describes the basic principles for assessing the effectiveness of jamming directed against an electronic network. The analysis is motivated by the rapid development of surveillance and command systems that can produce almost complete situational awareness. Traditional methods for jamming based on noise and repeated signals can be considerably improved by employing new methods based on saturation and deception. The object of this report is to assess the effectiveness of electronic jamming by quantitative analysis. The method is based on the assumption that a network of sensors will use the optimal procedure available to produce situational awareness. The analysis demonstrates that one can divide sensor systems into two groups: 1) rapid systems that automatically handle limited amounts of information; 2) complicated systems that work at a slower rate and handle large amounts of information combined with human knowledge. This division explains why methods of electronic warfare tend to be substantially different in these cases. Jamming of a network should be directed against situational awareness rather than individual sensors or communication lines. Intelligent jamming involving deception of decision makers and saturation of system operators is particularly effective. This conclusion agrees with experiments performed at the Swedish Fighter Control and Air Survelliance System (Stril).