The anime concerns an organised armed force, and its members. Said body should have both the equipment and hierarchy found in military groups, and should ideally be actively utilising their power against an opponent. Characters are either employed as professional soldiers or enlisted on a volunteer basis, for ideological reasons.
Note: Just because the anime contains a bunch of soldiers or a tank, unless that is actually what the anime is about, you might not want to add this genre.
Anime with this category, like anime with Military as category concerns an organised armed force, but with the difference that they should primarily conduct aerial warfare.
Note: Just because the anime contains a bunch of planes or similar, unless the anime is actually about a fighting airforce, you might not want to add this genre.
Feudal Warfare is the warfare of the Middle Ages and therefore the setting must take place in a time line similar to that of Middle Ages or its Asian/American counterparts, or in a fantasy world. Generally it can be described the same way as the Military category, just that the weapons used are swords, spears, bows, catapults, cannons and other weapons used in the Middle Ages.
Note: Just because the anime contains a guy or a couple of guys with swords wondering about, doesn't make it applicable for this category, unless there are larger military organizations/groups involved in armed conflict with each other, you might not want to add this genre.
As with Airforce and Military, this category is for anime that concerns an organised armed force, but it conduct naval or space warfare.
Note: Just because the anime contains warships, submarines or spaceships, unless it is actually about those armed forces, you might not want to add this genre.