Firstly for the size of their army they have ~1,280,000 active personnel (~4th, between US and Russia), 600,000 reserve and 5,700,000 paramilitary (overall 1st in the world with 7580000 personnel).
They have 5845 tanks (2nd in the world to Russia) and ~11920 artillery (2nd again to Russia)
They have 35 submarines (4th to Russia, USA and China)
The short border will be deadly, expect Seoul to be fully destroyed.
