作為宏大的軍事工程，長(zhǎng)城雖然既有通風(fēng)報(bào)信的烽火臺(tái)，又有城垛和甕城之類用作攻防的工事，但建成后，長(zhǎng)城的軍事功能在戰(zhàn)役中并沒有發(fā)揮多大作用。更多的時(shí)候，長(zhǎng)城以其強(qiáng)大的威懾力量，起到了嚇阻外敵侵?jǐn)_，避免戰(zhàn)爭(zhēng)的作用。在冷兵器時(shí)代，長(zhǎng)城的威懾作用是卓有成效的。在廣闊的草原、荒漠上，長(zhǎng)于騎射的游牧民族縱橫馳騁，銳不可擋。長(zhǎng)城的出現(xiàn)，使他們不得不勒住戰(zhàn)馬的韁繩，想方設(shè)法攻克長(zhǎng)城。但攻堅(jiān)步戰(zhàn)不是他們擅長(zhǎng)和習(xí)慣的作戰(zhàn)方式，于是，長(zhǎng)城這條橫亙?cè)隍T兵面前的高大墻體，消解了他們的銳氣，延緩甚至完全阻止了他們的鐵蹄揮師南下。

    秦始皇筑長(zhǎng)城，“卻匈奴七百余里，胡人不敢南下而牧馬?！?

    漢武帝(前141-前87年在位)，“建塞腳，起亭燧，筑外城，設(shè)屯戍以守之，然后邊境得用少安?！?

　　明成化七年(1473年)，延綏巡撫余子俊大規(guī)模修筑邊墻，“北虜知不能犯，遂不復(fù)入套”。

　　明隆慶五年(1571年)，由于邊墻加固，戒備加強(qiáng)，迫使俺答汗和明王朝簽訂《隆慶和議》。

　　戚繼光(1528-1588年)任薊鎮(zhèn)總兵后，修邊墻，筑敵臺(tái)，積極訓(xùn)練兵卒，蒙古朵顏等部曾打算入侵中原，但懾于戚繼光防御威嚴(yán)而未敢行動(dòng)，“薊門宴然”，數(shù)十年沒有戰(zhàn)事。

A Defense Work to Avoid Wars

　　As a massive military presence, the Great Wall was complete with watchtowers for relaying information and battlements and protective citadels for defensive purposes. The truth is that the Great Wall never had much opportunity to prove its military role in battles. Most of the time, however, it did serve the purpose of avoiding battles by scaring off any potential invaders.

　　In the years before firepower, the Great Wall had an obvious effect as a deterrent. It was impossible to hold in check nomadic peoples living on vast expanses of grassland and desert who were excellent at riding horses and fighting on horseback. However, for the nomadic tribes, fighting at close range to take a fortified defensive work was not something with which they were most comfortable. So the Great Wall forced them to pull back the reins of their horses and to try to come up with inventive ways to overcome it. Consequently, the mighty structure dampened their morale, slowed them down and even totally held them in check as they attempted to march southward.

　　The Great Wall built by the First Emperor of Qin “held off the Xiongnus from the territory for more than 300 kilometers, making them afraid to make any southward moves.”

　　Emperor Wu of the Han (r. 140-87 BC) had fortresses and watchtowers erected and an outer wall built. He dispatched troops to guard the wall and ensured stability along the border.

　　In 1473, Yu Zijun, a defending general in the Yansui region, engaged in massive construction on the border wall so that northerners dared not move near the area.

　　The year of 1571 saw the conclusion of the Longqing Agreement between the Tartar leader and the Ming court thanks to the strong and vigilant defense along the wall.

　　When General Qi Jiguang was made commander-in-chief of the garrison at Ji, he had walls and watchtowers built and drilled his troops, both cavalrymen and infantry soldiers. As a result of General Qi’s strong defensive display, the northern tribal Mongolians who had planned to invade the Central Plain never dared to put their plan into action. For dozens of years, the border enjoyed peace and stability.