A monk in mud-slick robes hefts a crate of dried roots and a lacquered box of needles onto a small ship. The captain grunts, and the monk folds a scrap of paper that names him a court doctor in a foreign land.
Baekje (백제) kept medical know-how like a state secret, and they shipped it abroad. The Japanese chronicle Nihon Shoki records that in the sixth century Baekje sent physicians, herbal formulas, and even medical books to the Yamato court. Those doctors landed in a court that paid them and gave them rank, so this was travel with a job, not charity.
Silla (신라) ran medicine as part of the state too. The Samguk Sagi (삼국사기) lists royal physicians and gives glimpses of how the kingdom handled epidemics. When plague hit, the court sent officials to inspect towns, treat the sick, and control grain for medicines. That looks a lot like early public health, with job titles and orders from the throne.
Archaeology backs the papers. Tombs from the Three Kingdoms period hold bronze probes, bone-setter splints, and pottery with traces of plant compounds. Skeletal remains show well-healed fractures that were almost certainly set and dressed by hand. Monks and state doctors both mixed chants with poultices, and moxibustion and acupuncture were in active use.
The whole scene is messy and human. Ships creaked in the rain. A court doctor from Goguryeo (고구려) or Baekje might be as likely to pull an arrowhead as to recite a sutra. Medicine then moved across borders the way soldiers did, by person-to-person trade, favor, and the odd royal decree.
So modern Korea's role in medical exchange has very old roots, with doctors who packed herbs and passports centuries before clinics and clinics had networks. Text someone this and watch them stare at how mobile and political health used to be.