Wireless sensor network can be used in military application for monitoring militant activities like tracking enemies, force protection and monitoring the vital signs of the soldiers who are in a battlefield.  Wireless sensor network has set of distributed sensor nodes which are connected to each other. These sensor nodes are low powered, low cost, small in size with limited amount of battery supply. While designing the wireless sensor network for sensing and data reporting task limiting the utilization of power resources of the sensors is the important concern in order to extend the lifetime of the wireless sensor network. The nodes which are selected as a mobile sink will quickly consume more battery power and degrade the network lifetime. Sink relocation is the most powerful method to extend the network lifetime without consuming more battery energy. In this paper, a survey of the existing distributed mobile sink routing protocols and the techniques for relocating sink to maximize the network lifetime with respect to the mobile sink routing protocol design requirements and its challenges are explained. With respect to the target applications ways to increase the battery efficiency and selecting the path with low cost by selective routing protocols are also discussed.