Well, the Deluge Region is marked by its unending torrent of rain, it never ends and it has always rained, meaning the people of the region, mostly those of Yuzhno-Karafuto, have had t odevelop according to their conditions.
First off, the Line Infantry of Yuzhno-Karafuto is professional and well armed. The Weapons are well constructed and advanced, especially in the way of loading the weapon so that rain doesn't spoil the powder.
The Line Infantry Uniforms are made up of rain resistant clothing of course, they wear hats (Think those straw pan hats, like in Vietnam or East Asia) to keep the rain out of their eyes. All weapons are adjusted to have bayonets, yet amazingly in the deluge region large exhanges of volelys still occur despite the rains effect. Still though, more often then not the battles are decided in armed combat.
Cavalry is nonexistant, useless in this enviroment, meaning the infantry lines are swelled with numberes. This also gives an advantage against foreign invaders whom must sacrifice their own cavalry units to the extreme weather.
Artillery is unique, while much of it remains mounted in the city as defensive batteries, the Yuzhno-Karafuto Military sports some impressive, light peices. These can be transported in numerous ways, able to switch between sturdy wheels to heavy floats allowing quick transportation, especially in the streets which are often flooded, making the transport of artillery important. not being needed to limber or unlimbered, they can actually be deployed and moved quickly... However, these small cannons do not handle grape shot well and in seige combat, the portable peices cannot bring down heavy walls... Still, they remain a great infantry breaking weapon.
Finallu, the Yuzhno-Karafuto is incredible. Possibly the only navy built for such weather, the ships range from wave huggers (low to the Surface) ships thats are hard to hit for bigger ships, and the navy sports medium and large ships quick and versatile, all unique in design, able to take on large qualtieis of water but remain afloat... I'm working on some designs but its complicated stuff.
While the army is not up to large invasions of far off foreign territories, the Yuzhno-Karafuto Navy is 1st rate and is as such can assert influence across the coast! Piracy in war time can swell the treasury and their merchant ships are top of the line.
This is the basic idea, what do you think? This of course is besides the architecture of the cities themselves which are impressive considering the conditions.