장보고
A science documentary by EBS reported that "Jang Bogo"-class submarines will undergo major generational overhaul and refit every eight to twelve years. The overhaul and refit involves periodic cutting, complete disassembly, and re-welding of the hull for the upgrade or total replacement of the submarine's old engines, navigational equipment, batteries, and other essential equipment with their modern counterparts. Hull stretch may also have taken place in some of the "Jang Bogo"-class vessels since the early 2000s, but it has neither been completely confirmed nor denied. Some "Jang Bogo"-class vessels are demonstrated to have sub-Harpoon launching capability when previously the class was lacking it. ROKN is committed to build and maintain a submarine force of 26 attack submarines until 2025, excluding small and midget submarines, though it is not clear how many submarines among those will belong to the "Jang Bogo" class. The oldest commissioned "Jang" "Bogo-"class submarine by then will be 32 years old.