In the context of the Colombian armed conflict, the army is responsible for conducting control operations in challenging terrains where illegal armed groups operate. These operations face significant risks, including surprise attacks that may result in temporary or permanent injuries, loss of fundamental rights, and, in some cases, death. Therefore, it is crucial to equip army personnel with tools that enhance the security of communities and reduce the negative impacts of risky situations, such as ambushes. This study describes the design of the Tactical-Passive Early Warning System (SATP), created to assist mobile patrols in control operations, involving the development of two prototypes: SATP-1 and SATP-2. The SATP-1 provided data that informed the creation of the improved SATP-2 system, which utilises passive infrared (PIR) sensors and radio frequency communication. This portable and low-cost system is easy to use in the field. Testing demonstrated excellent performance, with a night-time detection rate of 94.2% and a 93% detection rate indoors under intense lighting conditions. Such developments can also be applied to other fields requiring high levels of security in complex or expansive areas, such as the agriculture sector.