Those aren't strategic bombers. The one in front is an AC-130 gunship with an external fuel tank on each wing. The one in back is either a C-130 (cargo transport), HC-130 (search and rescue or combat search and rescue), KC-130 (aerial refueling), or MC-130 (special ops, various mission types), with 2 external fuel tanks on each wing. Based on the kinda weird shading on the nose making it look less round and more chisel shaped, I'm guessing an MC-130, since they have noses like that (while the MC-130 isn't a strategic bomber, it is capable of dropping the GBU-34/B MOAB). The only operator of the AC-130 and MC-130 is USA - there's no foreign sales of either - both under the Air Force Special Operations Command, and as far as I can tell, the wings they're associated with are based in the US (in Air Force bases in New Mexico and Florida). Why would these be anywhere near South Korea? How would they even get there in the first place? There's like 9000+ miles of ocean they'd need to cross if going from the west coast, and their range is 3000 miles at best, better with aerial refueling, but unless they're taking a page from Operation Black Buck, I just don't see it happening.