Public safety and emergency response organizations increasingly rely on wireless technology to provide effective command, control, and communication during emergencies and disaster response operations. However, in the event the public mobile network infrastructure is damaged, distressed or destroyed, as occurred during the events of 9/11 and Hurricane Katrina, first responders need a reliable, backup solution that allows them to continue to use full cell phone capabilities. This paper describes a novel portable Advanced Mobile Communications System (AMCS), the heart of which is a Tactical Base Station Router (TacBSR) that encapsulates all cellular network functions in a single box. It represents the smallest form factor in the industry (i.e., smaller than a laptop). The result of 6 years of development in Bell Labs, the TacBSR does not require any pre-existing wireless infrastructure, providing capacity and coverage on demand.