The threat from a limited attack of long-range weapons (missiles) on a short term and on a long term is outlined. The base for the defence against this threat is a surface covering network of sensors. The anti-missile/aircraft defence is composed of two systems, one short-range system for the defence of critical objects, and one longrange system for the defence of areas and indirectly the critical objects. The positioning of the weapon systems is discussed focusing on the area-covering missile or unmanned aeroplane system and the safely protected area is calculated taking the capacity of the sensor network and the missile system into account. The study has given some simple tools treating the importance of the weapon base position in relation to the detection surface of the attacking missiles and of the relation between the velocities of the two missile systems.