One of the biggest challenges in current defence scenario is significant improvement in countermeasure, which essentially leads to the degradation of classical guidance laws that are most widely used in practice. To improve the odds of intercepting an intelligent target and destroying its warhead, a salvo attack of two or more interceptors could be considered as a viable option since it is more difficult to create an effective countermeasure against a group of interceptors attacking at the same time, even though each of them may follow some conventional guidance strategy. Moreover, this simultaneous salvo attack can also be further improved in efficiency by incorporating the shoot-look-shoot approach in making decision about launching of interceptors. This can be considered as the first step towards a layered defence system, which has been described in literature as a potentially effective strategy against short range or long range ballistic threat. Thus, in strategic defence scenario, cooperative salvo of interceptors has a great role to play. Also, ballistic and cruise threat is a present day reality. This paper discusses a cooperative strategy for lower speed interceptors guided by Retro-PN guidance law to perform salvo attack against a higher speed target. The effectiveness of this cooperative strategy is justified with simulation results. © 2014 IFAC.