This paper discusses the impacts of the navigation accuracy and sensor accuracy on combat vehicles and some potential improvements. Two of the combat vehicle subsystems are the fire control subsystem for weapon engagement and the target locating subsystem for fire support. The fire control subsystem is required to comply with the hit probability requirements that depend on position sensor accuracy, rate gyro sensor accuracy and the Euler angle accuracies of the Inertial Navigation Unit (INU), in addition to many other factors. The paper reviews the kinematic lead correction estimation and its error sources. Rate gyro sensors are widely used in the target Line of Sight (LOS) stabilization and the weapon Line of Fire (LOF) stabilization. This paper presents a solution that can remove the components in the rate gyro signals related to earth rotation rate and trim down the fire control subsystem drifting errors significantly. Fire control subsystems also use the pitch and roll angles of an INU for LOS and LOF cant angle correction, so no cant sensor is needed. The target locating subsystem needs to meet Target Location Error (TLE) requirements that rely on the Euler angle and position accuracies of an INU, the Global Positioning System (GPS) positioning accuracy, the target range measurement accuracy and the angular position sensor (measuring the LOS angles) accuracies. The error sources of the target locating subsystem discussed in this paper are the INU/GPS position errors, the INU Euler angle errors (especially the heading/azimuth error), the Universal Transverse Mercator (UTM) based target location computation errors, and the target range error. Based on these insights, this paper provides some improvements on the target locating accuracy. This paper concludes that the navigation systems and the sensors can be improved or upgraded for better fire control subsystem and target locating subsystem performances. Some of the insights and improvements presented in this paper can be applied to many combat vehicles to enhance their lethality.