Warrior angels primarily take care of external affairs, both in fighting down hell creatures and other enemies of Heaven, but also in more peaceful matters such as diplomacy or civilian aid outside Heaven.
Heaven does not operate with any forced recruitment of soldiers, employment in the army is voluntary.
Warriors are mainly trained in sword fighting since bows or handheld firearms don't do enough damage to kill most demons. Also, mortals who see angels in action must not be exposed to higher technology than they already possess. While this rule applies to all items angels bring into mortal worlds, it is especially important on the topic of weaponry.
Warrior angels are distinguished by four major ranks, but individual angels in either group can be ranked more specifically.
Furthermore the special group of angels called seraphim are also seen as part of the military, despite that they rarely fight alongside the actual warriors. Seraph is the rank above general.
Heaven's spies are another group that is not considered a real part of the military, but is an important asset in many military operations regardless.