One thing I do sometimes is to take characters from unrelated fiction and use them as a template (changing name, etc.)
So for example, I need a naval officer to command a battle. I thinly base him off Benjamin Sisko from Deep Space 9. Career military, has a son, lost wife to Wolf 359 previous war. Currently taking offensive stance so that in this war battles are fought in enemy terrain, not at home where they endanger his people. By extension, willing to inflict heavy losses on the enemy rather than risk taking them. Reacts poorly to heavy losses among his people. Holds in contempt other commanders (allied or enemy) willing to expend large numbers of troops for an objective but will take advantage of an enemy who does so.
D for Drakensis
You're only young once, but immaturity is forever.
So for example, I need a naval officer to command a battle. I thinly base him off Benjamin Sisko from Deep Space 9. Career military, has a son, lost wife to Wolf 359 previous war. Currently taking offensive stance so that in this war battles are fought in enemy terrain, not at home where they endanger his people. By extension, willing to inflict heavy losses on the enemy rather than risk taking them. Reacts poorly to heavy losses among his people. Holds in contempt other commanders (allied or enemy) willing to expend large numbers of troops for an objective but will take advantage of an enemy who does so.
D for Drakensis
You're only young once, but immaturity is forever.