However, the collapse of the North Korean regime and unification by Seoul would also present a number of problems for PRC. A sudden and violent collapse might cause a mass exodus of North Koreans fleeing or fighting poverty into PRC, causing a humanitarian crisis that could destabilize northeast PRC. The movement of South Korean and American soldiers into the North could result in their being temporarily or even permanently stationed on PRC's border, seen as a potential threat to PRC sovereignty and an imposition of a PRC containment policy. A unified Korea could also more strongly pursue its territorial disputes with PRC and might inflame nationalism among Koreans in PRC. Some have claimed the existence of contingency plans for PRC intervening in situations of great turmoil in North Korea (with the Chinese Academy of Social Sciences' Northeast Project on the Chinese identity of the Goguryeo kingdom potentially used to justify intervention or even annexation).