第二次鴉片戰(zhàn)爭時期的第三次大沽口之戰(zhàn)，始于咸豐九年十月 (1859年11月) ,英法政府為了對第二次進攻大沽口的慘敗進行報復，分別再次任命額爾金、葛羅為駐華公使，征調(diào)大批艦艇，組成新的英、法聯(lián)軍，由英海軍上將賀布、陸軍中將格蘭特、法陸軍中將孟托班，任艦隊正、副司令，繼續(xù)擴大侵略戰(zhàn)爭。
咸豐十年六月(1860年7月),英艦173艘，法艦30艘，載兵25000人，駛至大沽口外水域，停泊于大沽與北塘間距岸8里的海面上。這時大沽口防線上清軍有10000余人，分別駐守于大沽南、北炮臺和草頭沽、于家堡、新河、新城、塘沽、營城一帶的營盤內(nèi)，仍由僧格林沁督率。大沽炮臺又增加了從沉水敵艦中撈出的洋炮12尊；大沽村外挖濠溝一道，塘沽筑壕墻一道，?？谠鲈O萬斤鐵戧，營城新筑炮臺4座。當英、法的龐大艦隊駛抵大沽口外時，僧格林沁認為，只要加強炮臺正面防御，便可萬無一失，并向朝廷保證，“此次決戰(zhàn)，必操勝算” 。
清政府對戰(zhàn)局依然心存疑慮，希望通過美、俄調(diào)停，讓英、法公使從北塘登陸入京換約，并發(fā)出在北塘為公使登岸讓出一條通道的命令。僧格林沁則認為，北塘營壘過于靠近民居，不易防守，堅持主張全面撤除北塘防務。于是 “北塘的炮位兵丁悉數(shù)撤去” ,把撤出的大炮、兵丁布置在大沽、營城一帶。
停泊在大沽口外海域的英、法艦隊，鑒于上次失敗的教訓，這次未敢輕易從正面進攻炮臺，而是伺機尋找炮臺大炮射程之外的登陸地點。策劃從背后包抄炮臺。俄國新任公使伊格那切耶夫暗地向英、法聯(lián)軍透露了 “北塘防務空虛” 的情報。英、法艦隊決定乘虛從北塘登陸。

·1860年8月1日，英、法侵略軍占領(lǐng)北塘炮臺

六月十六日 (8月1日)下午，英、法艦船30余艘、軍隊5000人，乘海潮偷偷從北塘登陸，并順利地把炮車、馬隊運上北岸，迅即侵占了已經(jīng)撤防的北塘炮臺。英、法侵略軍占據(jù)北塘鎮(zhèn)，大肆對居民進行殺戮搶掠。
六月二十六日 (8月12日),聯(lián)軍萬余人，分頭向塘沽以西的新河、軍糧城進攻。僧格林沁從塘沽和新河，抽調(diào)2000余馬隊進行迎擊。聯(lián)軍排成散兵以排槍阻擊馬隊沖鋒，炮車又集中炮火連續(xù)轟擊，清軍馬隊幾乎全軍覆沒。六月二十八日(8月14日),聯(lián)軍進攻塘沽，激戰(zhàn)2個小時，占領(lǐng)了塘沽壕墻，清軍退守到大沽北炮臺。七月一日 (8月17日),聯(lián)軍從大小梁子渡過海河到達南岸，包抄南炮臺的后路； 同時，海上的敵艦也從正面進逼。大沽各炮臺陷于前后夾擊的危險境地。此時僧格林沁已喪失抗擊信心，對南北炮臺“能否扼守，實無把握” 。轉(zhuǎn)天，直隸總督恒福向聯(lián)軍求和，遭到拒絕。七月五日 (8月21日)晨，聯(lián)軍傾巢而出，攻擊北岸炮臺。炮臺守軍英勇作戰(zhàn)，奮力抵抗，各炮臺一齊開炮策應。激戰(zhàn)到上午10時，炮臺的彈藥庫被擊起火，北炮臺失陷。這次戰(zhàn)斗斃傷敵人200余人； 清軍傷亡1000余人，提督樂善犧牲。北炮臺失陷后，僧格林沁棄陣而逃，連夜逃回通州。直隸總督恒福以避免居民受損為借口，拱手向聯(lián)軍讓出南岸各炮臺，大沽口防線全面崩潰。
The third Dagu battle took place in November 1859(the ninth year of Emperor Xianfeng). To revengetheir defeat,Britain and France appointed Lord Elginand Gloria as their respective ambassadors to lead thenew allied forces in warships. The UK admiral Hope,Lieutenant General Grant,and the French LieutenantGeneral as commander general and deputy commandersgeneral were send to expand the war of invasion.
In June 1860,173 British warships and 30 Frenchwarships carrying 25,000 soldiers arrived at the opensea of the Dagu Emplacement,eight miles away fromBeitang. At the Dagu line of defense,10,000 soldiersunder the leadership of Sengge Renchin stationed atDagu north and south emplacements and the barracksof Caotougu,Yujiabao,Xinhe,Xincheng,Tanggu andYingcheng. The Dagu Emplacement was reinforced withthe 12 cannons fished out from the sunken warshipsof the enemies. A trench was dug out for Dagu; a wallwas built for Tanggu; an iron block of 5,000 kilogramswas put at the seaport; and at Yingcheng,four newfortifications were constructed. When the allied forcesarrived,Sengge Renchin promised the Qing Court thatthe front defense of the emplacement would ensure the success.
But the Qing royal government was still worried.They wished that British and French ambassadors wouldgo to Beijing by Beitang for treaty exchange via Americaand Russia`s intermediation. They also issued a passfor the ambassadors by Beitang. According to SenggeRenchin,battalion of Beitang,near civilian houses,was not suitable for defense,so he ordered to retreatthe cannons and soldiers and placed them at Dagu andYingcheng.
Because of the previous failure,the British andFrench fleets did not attack the emplacement directly.They wanted to land out of the cannon shot and outflankthe emplacement. The Russia`s new ambassadordisclosed Sengge Renchin`s retreat from Beitang,so theBritain-France army decided to take the advantage of the weakness.
In the afternoon of August 1,5,000 enemysoldiers by 30 warships landed Beitang while tiding.They carried cannons and horses to the north bank andoccupied the emplacement quickly without meetingresistance. They robbed and killed many civilians there.
On August 12,about 10,000 enemies attackedXinhe and Junliang cheng,which located south ofTanggu. Sengge Renchin drew 2,000 cavalries fromTanggu and Xinhe for counterpunch,but all of themwere killed by the guns and cannons. On August 14,theenemies broke through the walls at Tanggu in two hoursand the Qing army retreated to the Dagu Emplacement.On August 17,the enemies crossed Meihe River andreached the south bank and their warships attacked inthe front. The Dagu Emplacement was under blanketattack. Sengge Renchin lost his confidence of resistance.On the next day,Heng Fu,Governor-General of Zhili,sued for peace but was denied. At the dawn of August21,the enemies turned out in full force when attackingthe north emplacement but met with courageousresistance from the defending troops with support fromthe other emplacements. At 10 am,the ammunitiondepot was on fire and the north emplacement lost. Twohundred enemies were killed but 1000 Qing soldiers diedincluding Governor Le Shan. After the loss of the northemplacement,Sengge Renchin fled to Tongzhou for lifeat night. With the excuse of protecting civilians,HengFu gave up the south emplacement and the Dagu defenseline broken down by the allied invaders.

·1860年8月1日，英、法侵略軍占領(lǐng)北塘炮臺