With the development of unmanned aerial vehicles (UAVs) in both hardware technology and theoretical approaches, UAVs begin to emerge as important potential equipment for future communication networks, where UAV-assisted emergency communication attracts the most attention due to the flexibility and mobility of UAVs. In this paper, we consider a remote emergency scenario with the ground base stations (BSs) being destroyed and study the access and backhaul link optimization problem. We propose a joint user association, UAV positioning, and resource allocation (UPR) algorithm to maximize the system throughput. We deploy UAVs not only as BSs to provide access links but also as relays to provide backhaul links, where the transmission rate of the system depends on the minimum of all the transmission links. We theoretically analyze the maximization problem of the system throughput and derive the optimal resource allocation for all the transmission links. We also prove the optimality of the equidistant alignment of UAV relays and their linear alignment with the emergency vehicle and solve the resulting optimization problem by alternating between the positioning of UAVs and user association. Simulation results verify the effectiveness of the proposed UPR algorithm.