There is ungodly amount of garbage history military history out there, because people want to read it. However, that does not mean there is not a huge amount of great work done in that field.
Its quite simply the case that for 1000s of years states major spending was on military and military matters, and the greatest transformation of society and economics happen during conflicts. Trying cut out military history from other fields is a fundamental mistake of the modern historians and more importantly universities.
I often listen to lectures from military historians and they quite often have a 'black sheep' feel around them, making self-depreciating jokes about how they still exist, this often leads to good lectures because they are already not inhibited by the conventions and trends other historians tend to follow.