Since few systems exist in isolation, a key question is how a system responds to an environmental forcing. Whether we think about how the brain can encode information, a fish detect food in muddy waters, or an advertiser influence the market, this very general challenge spans different disciplines and is dealt with by the adoption of different strategies. Nevertheless, those strategies basically fall into one of two categories: either to increase the strength of the external forcing, or to optimise the capability of the system to respond to the signal. This last strategy is the object of this thesis: specifically, we will show that extended systems that interact via a combination of attractive and repulsive links are able to optimise their response to an external forcing, for some fraction of repulsive links. Thus, the title Divide and Conquer in analogy with the ancient Roman strategy of controlling populations with a not so big army by dividing the subjects one against another.