Commander Sun Jianjun, originally of the Illuminated Precincts Dragon Army garrison, is now Commander of the SouthEast Wall Defense Region.
Commander Sun is investigating the Southern invaders, and trying to thwart them/him.
An Old Buddy Told Li Merit
Commander Sun is technically Commander of the SouthEast Wall Defense Region of the Dragon Army. As such, he currently has 10 chariots of the Dragon Army under his direct command. (A chariot is the basic unit of military in the country level army mechanic. For scale, Li Merit probably knows the Butterfly Kingdom has something on the order of 5 chariots of land forces total, but almost that much more in naval forces.)
He's an old school soldier, having slowly worked his way up the ranks from the infantry. He's got some family connections in the Savanna (Clan Jegal), which helped him get several of his early promotions, but since then he's pretty much self-made. The Dragon Army is his family now, and he's quite serious about protecting his men, while fulfilling their duties.
In the field, should it come to that, he's probably a star on defense, and much less effective on offense.
He's known to have recently had a bit of friction with Commander Teng of the SouthWest Region, as Teng managed to snag the Bearers of Swift Response (an elite commando unit based on the southern wall) from his command just over two years ago. The two commanders have not worked well together since.
He's also said to have a pretty extreme disdain for Commander Lo Ping of the NorthEast Region, so it seems he's really not good at making nice with his nominal peers, being unwilling to "play for points" as they say.
Personally, Comamnder Sun is known to be quite smart, and frequently inventive when it comes to getting around obstacles. This has earned him some minor feuds with various members of the higher-echelons, as well.
This, combined with his friction-filled dealings with his peers, means the common wisdom is that his career is likely capped at regional commander for political reasons. He's unlikely to mind though, as he'd probably think once you get higher than that, the Dragon Army does turn into a political beast far more than a proper military machine.