长城词典·镇城明代长城实行镇守制度，长城沿线分为“九边十一镇”。镇是长城的最高军政管理机构，其下管辖若干路。镇城是各镇总兵所驻扎的军事指挥中心。河北境内有蓟镇、昌镇、真保镇和宣府镇，分别驻迁西县三屯营、昌平县长陵、保定和宣化城。三屯营和宣化城都是为保卫长城专门营建的镇城。 Great Wall dictionary·Garrison TownIn the Ming Dynasty，garrison system was widely implemented in guarding the Great Wall，which was divided into “nine borders and eleven towns” along its line. Garrison town was the most superior military and political administrative authority of the time，and it governed a number of subordinate barracks. Garrison town was the military command center where commander of each garrison troop was stationed. In Hebei，Ji Zhen，Chang Zhen，Zhenbao Zhen and Xuanfu Zhen barracks were respectively stationed at Santunying（ Qianxi County），Changling（ Changping County），Baoding and Xuanhua. Santunying and Xuanhua were garrison towns built specially for defending the Great Wall.
