(covers information from several alternate timelines)
A military log is a form of log entry record keeping. It is used occasionally for logging the location of individuals.
In an alternate timeline, during the Federation-Klingon War, Federation starships, such as the battleship USS Enterprise-D, recorded military logs. This log had replaced the traditional captain's log, and was recorded in terms of combat-dates rather than stardates. (TNG: "Yesterday's Enterprise")