明末清初的學(xué)者顧炎武(1613-1681年)在論及幾個(gè)王朝覆滅前發(fā)生在居庸關(guān)一帶的戰(zhàn)事時(shí)，感慨地說(shuō)：“地非不險(xiǎn)，城非不高，兵非不多，糧非不足也，國(guó)法不行而人心去也?！比诵囊蝗ィv有長(zhǎng)城漫漫、雄關(guān)重重，又哪里能守得住風(fēng)雨飄搖的江山呢?

　　用長(zhǎng)城作屏障，早在春秋(前722年-前481年)諸國(guó)爭(zhēng)霸的時(shí)候就有了，為了防御入侵，各諸侯國(guó)紛紛大興土木，相繼建起了長(zhǎng)城，但最終都未能依仗長(zhǎng)城而逃脫被秦國(guó)翦滅的命運(yùn)。

　　秦始皇(前221-前210年在位)一統(tǒng)宇內(nèi)，自以為功蓋三皇，業(yè)冠五帝，于是忘乎所以，令蒙恬北擊匈奴，督修萬(wàn)里長(zhǎng)城，以防“胡”滅秦。最終的結(jié)局卻是，長(zhǎng)城修完了，秦朝的江山社稷也瓦解了。

　　自秦朝以后，幾乎每朝每代都在維修和擴(kuò)建長(zhǎng)城，夢(mèng)想以此來(lái)鞏固自己的寶座?？蓮膩?lái)就沒(méi)有哪位真龍?zhí)熳幽軌蛉缭敢詢敗?

　　北魏明元帝(409-423年在位)泰常八年(423年)，整修了東起赤城(今河北赤城縣)西至五原(今內(nèi)蒙古包頭市西北)的長(zhǎng)城二千余里，并在沿線要地設(shè)置六個(gè)軍事重鎮(zhèn)?？墒?，長(zhǎng)城尚未修完，這六個(gè)地方就已經(jīng)燃起了熊熊烈火，但不是長(zhǎng)城抵御外敵的狼煙，而是六鎮(zhèn)兵民起義的烽火。這段專制者倒臺(tái)的歷史雖與長(zhǎng)城有關(guān)，但在數(shù)千年波翻浪涌的歷史長(zhǎng)河中不過(guò)是幾圈不起眼的漣漪。

　　修長(zhǎng)城最賣力的是明太祖朱元璋(1368-1398年在位)的子孫們，他們歷經(jīng)270余年，對(duì)長(zhǎng)城進(jìn)行了18次大規(guī)模修復(fù)，幾乎是在秦長(zhǎng)城的基礎(chǔ)上重修了一遍，構(gòu)成了“層層布防”的縱深防御體系，沿線陳兵90余萬(wàn)，稱得上“寸土設(shè)障，步步為營(yíng)”。在重要的關(guān)口，尤其是在當(dāng)時(shí)的都城-北京居庸關(guān)一帶，層層筑起堅(jiān)實(shí)高大的城墻。然而，這看起來(lái)固若金湯的長(zhǎng)城防線，也數(shù)度失守。明正統(tǒng)十四年(1499年)，瓦剌首領(lǐng)也先率眾攻破長(zhǎng)城，在土木堡(今河北懷來(lái)東)俘虜了“御駕親征”的英宗皇帝朱祁鎮(zhèn)(1436-1449、1457-1464年在位)。嘉靖二十九年(1550年)，韃靼首領(lǐng)俺答又率眾攻入薊鎮(zhèn)地區(qū)，從古北口向南，直抵北京城下。1644年，李自成率領(lǐng)的農(nóng)民起義軍揮師突破居庸關(guān)，幾天后便攻進(jìn)北京城，宣告了明王朝的覆滅。

What the Great Wall Could Not Do

　　Gu Yanwu (1613-81), a scholar active in the late Ming and early Qing dynasties, said in commenting on the warfare in the vicinity of the Juyong Pass on the Great Wall following the demise of several dynasties:

　　“It was not that the terrain was not precipitous, nor was the wall not tall enough; it was not that there were not enough soldiers or the grain supply was inadequate. The rule of the country, however, could not last long because the rulers had lost the heart of the people.”

　　Once losing the support of the people, rulers could not prevent the fall of their dynastic rule, despite the long and towering defensive work in the form of the Great Wall.

　　The practice of using the wall as a defensive work began during the period when warring states contended with and tried to annex one another during the Spring and Autumn Period (772-481 BC). They all had defensive walls built but in the end none of them were able to use the wall to keep off the wave of soldiers of the State of Qin.

　　The First Emperor of Qin who ruled from 221 to 210 BC, once becoming the national ruler by defeating all other states, lost the sense of who he really was and thought he was greater than all previous rulers. He ordered General Meng Tian to fight the northern tribe of the Xiongnu and had a very long wall built to defend against the possible onslaught of the Xiongnus. The outcome was that the completion of the Great Wall was accompanied by the fall of the Qin Dynasty (221-206 BC).

　　After the Qin, almost every ensuing dynasty maintained, repaired and expanded the Great Wall in the hope of consolidating its rule. None of the “sons of heaven,” however, had the good fortune of achieving his goal.

　　Emperor Mingyuan, who ruled the Northern Wei from 409 to 423, launched the most massive construction of the wall in 423 when he had more than 1,000 kilometers of the wall repaired or built between present-day Chicheng in Hebei Province in the east to Baotou in Inner Mongolia in the west. He reinforced the system of defense with the establishment of six major military towns along this section. Soon, fire, however, was lit in these six strategic towns, not to signal a fight against northern invaders but to sound the battle cry of rebellious soldiers and residents.

　　Though the fall of the Northern Wei ruler had something to do with the Great Wall, it was nevertheless a rather small incident during the long history associated with the wall. The most enthusiastic wall builders were the sons and grandsons of the founding emperor of the Ming Dynasty Zhu Yuanzhang (r. 1368-98). During a period of 270 years they launched massive repairs of the Great Wall on 18 occasions, virtually turning it into an entirely new wall and an impenetrable system of defense guarded by some 900,000 troops. “Every inch of land was guarded and every step was protected” was an apt description. Strategic mountain passes, particularly the Juyong Pass that guarded the entrance to the capital city of Beijing, was reinforced with several layers of thick and towering walls. The defense seemed secure, but the fact is that the wall was lost to the enemy several times. In 1499, the northern invaders while attacking the Great Wall captured none other than Emperor Yingzong (r. 1436-49; 1457-1464), who had come to the front to personally lead the defense. Then in 1550, the ancient Tartars, under the command of Anda, fought their way through the Gubei Pass to the city wall of Beijing. On March 15, 1644, Li Zicheng, leader of a peasant rebellion, broke the defense of the Ming troops at the Juyong Pass and three days later, entered Beijing, putting an end to the Ming Dynasty.