Battle of Baekgang
Much of the debate over these fortresses began in the late Meiji period (1868–1912) and early Taishō period (1912–1923), when geography and archaeology took off in Japan for the first time, and the classification of "kōgoishi" fortresses emerged. One key element of the debate was, and continues to be, whether these fortresses were built in the late 7th century, following Japan's defeat in the Battle of Baekgang, as defenses against a possible Silla–Tang invasion of Japan, or whether they were built earlier, possibly independently from the policies or orders of the Yamato court. During the first decades of the 20th century, a vibrant discourse was expounded regarding the time these fortresses were built, their similarities to one another and to Korean structures, the way in which they spread, and the reasons they were built. This debate continues among archaeologists today.