Two-step floating catchment area (2SFCA) indices serve to measure accessibility in a geographical area. They were developed mainly to investigate the distribution of medical resources to civilians. Recently, the 2SFCA methodology was introduced to a militarybackground where accessibility of field hospitals along a frontline is considered. This article aims to develop a new composite index with a clear interpretation that allows accessibility to be compared for two distinct situations in the following setting. In thefirst situation, accessibility is calculated and then the situation changes which impacts accessibility as well. The composite index that is developed in this article then interprets the change and assigns to it an interpretable numerical value. The final composite index isa weighted mean of eleven properties of accessibility indices. Furthermore, the developed index is appropriated for the use in military environment to investigate the distribution of field hospitals along a frontline.