This paper proposes and analyzes an efficient cooperative relaying selection scheme (eCoRSS) based on time division multiple access (TDMA) in tactical multi-hop wireless networks (TMWNs). In TDMA, each user shares the same frequency channel and is assigned to a different time slot. However, during a user¡¯s own time slot, if there is no forwarded packet in its queue, that time slot is wasted. eCoRSS uses idle neighbors between a source node and a relay node to serve as assistant nodes for the relay node if those idle neighbors receives packets from the source node successfully. As a result, multiple packets can be forwarded to a sink during one time slot without increasing the delay time. Moreover, since the proposed scheme is being considered in a mobile network, after calculating the link signal-to-noise ratio (SNR) values from node to node by a source node, eCoRSS defines a dynamic SNR threshold to compare with the node-to-node SNRs and decide which node qualifies for an assistant node. The simulation results demonstrate that eCoRSS significantly outperforms the previous scheme in terms of throughput, end-to-end delay, and energy consumption.