南宋偏安东南所形成的海疆形势和立国态势使得海防在南宋的国防格局中具有事关全局的地位。为了应对来自海上的军事威胁 ,南宋政府加强了对海防的统一领导 ,设立了沿海制置司。在防御上 ,实行了以海上防御为主的海防战略 ,在沿海建立了多支水军 ,并建立了相应的警戒和通信系统 ,同时又依靠巡检、县尉等其他政府武装以及民间武装 ,在千里海岸建立起了严密的防御体系。南宋在海防上采取的措施和战略保证了东南沿海地区长期的安全 The formation of the sea border and the nation-building trend in the southeastern part of Southern Song Dynasty made the defense of Haiphong a status of overall concern in the national defense pattern of the Southern Song Dynasty. In response to the military threat from the sea, the government of the Southern Song Dynasty strengthened unified leadership over Haiphong and set up the Coastal Division. In terms of defense, the coastal defense strategy based on maritime defense has been implemented. A number of naval forces have been established along the coast and corresponding warning and communication systems have been established. At the same time, they have also relied on such other government armed forces as patrolling and county lieutenants, as well as civilians armed forces, In Trinidad coast to establish a tight defense system. The measures and strategies adopted by the South Song on Haiphong ensure long-term security in the southeastern coastal areas