Battle of Lạng Sơn (1979)

The initial attacks was marked by Chinese artillery fire into Lạng Sơn at 05:00 on 17 February. The Chinese had paved way for their offensive throughout the night before by infiltrating the Vietnamese territory, cutting telephone lines and conducting sabotages.[9] Waves of PLA troops from the 55th Army quickly overwhelmed Hill 386, a position situated 1.5 km south of the border, killing 118 Vietnamese.[11] Though pockets of resistance were continued near the Friendship Pass and in Đồng Đăng, most of the Vietnamese defense was by then undertaken south of the town by the VPA 12th Regiment at the hamlet of Thâm Mô and its vicinity.[11] After taking Hill 386, the PLA used the 163rd Division to capture Đồng Đăng and strike Vietnamese positions on the Thâm Mô line.[12][13] The attack was backed by small groups of tanks arriving on Highway 4A. Fighting over the Thâm Mô area raged until 22 February, as Chinese charges in mass formations had been continuously repulsed with heavy casualties.[14] The Chinese field commanders had to switch their tactics, using small-unit attacks to flank Vietnamese positions instead of frontal attacks by human waves. The change resulted in the fall of Thâm Mô to the hands of the PLA 163rd Division at 20:00.[15] Đồng Đăng was taken on the next day.[16]

Similarly, Chinese massed attacks to the east of Thâm Mô on Thâm Lũng, which had started from 17 February, were stiffly contained by the defenders. On 18 February, a Vietnamese counter-attack launched by the VPA 2nd Regiment drove PLA units back to their assemble positions on Hills 409, 611, and 675; this pattern was repeated on the following days. On 23 February, the PLA stormed Phai Môn, a position to the east of Thâm Lũng, using six waves of attacks, of which all were rebuffed. Chinese forces had to launch twelve more charges throughout the day to finally break through Thâm Lũng, allegedly suffering over 1,000 killed.[17] At Cồn Khoang, a village in the rear of Hill 339, the Vietnamese 63rd Company had fended off the assault of an unevenly outnumbering Chinese force on 17 February, virtually wiping out an enemy battalion.[15]

From 24 to 26 February, fighting downscaled, as the PLA was holding back and regrouping. Two fresh Chinese divisions from the 54th Army, the 160th and 161st, moved up to spearhead the attacks, with the 55th Army behind preparing to advance toward Lạng Sơn. In meantime, the VPA 3rd Division had pulled out its troops from Thâm Mô to establish a new defensive perimeter between Cốc Chủ and Hill 417, on the western side of Highway 4A near Thâm Lũng, in order to keep the highway blocked, as well as to stand up to Chinese pressure from Thâm Lũng.[17] On 24 February, the VPA 1st Military Region Command officially established the Lạng Sơn Front with Major General Hoàng Đan in charge.[3]

At 06:05 on 27 February, Chinese forces renewed their offensive in Lạng Sơn[17] with a four-pronged attack on Hill 417, Khau Ma Son, Pa Vai Son, and Khau Khao Son, giving friendly units time to encircle Lạng Sơn from the southeast and southwest.[18] Khau Ma Son, a strategic 800-meter height located 4 km west-northwest of Lạng Sơn that virtually obstructed all major roads near the town, fell to a Chinese unit at about 14:00. Chinese control over Khau Ma Son made Vietnamese defense from Coc Chu to Hill 417 exposed to enemy's sight, as well as threatened VPA 12th Regiment's positions near Choc Vo.[17] However, the Vietnamese reacted promptly, retreating from the Coc Chu – Hill 417 defensive line to a group of positions between Quán Hồ and Kéo Càng, thus blocking the highway access to Lạng Sơn once again. The VPA command also reinforced their battered 12th Regiment by deploying the 42nd Regiment/327th Division to Kỳ Lừa, which was about 1 km north of Lạng Sơn, to face off the approaching PLA 43rd Army. Yet the remainder of the VPA 327th Division were still stationed further to the south at Chi Lăng to prevent any possible deeper Chinese intrusions. Other regular reserves, including three divisions of the 1st Corps (the 308th, 312th, and 320th-B), were also assembled south of the Kỳ Cùng River to protect Hanoi, leaving the task of defending Lạng Sơn City to the 3rd Division and the 42nd Regiment alone.[19]

From 28 February to 4 March, Chinese troops tried to push toward Lạng Sơn in a series of heavy engagements occurring to the north of the city.[19] As the Chinese attacked, they also managed to take control over all the roads connecting with Lạng Sơn, thus employing Mao Zedong's strategy of "the countryside surrounding the city" in order to avoid a Vietnamese trap of a "second Verdun".[20] By 28 February, they had captured all key positions that shielded Lạng Sơn from the northeast, including Khau Lau Son, Khau Bo Son, Khau Tang Son, and Pa Vai Son.[21] Though seriously weakened, the Vietnamese 12th Regiment had not given up contesting Chinese troops along Highway 1B, with battalions and companies relentlessly defending Hills 607 and 649. On 2 March, a Chinese column on the highway was ambushed by a Vietnamese battalion. During the period of 2–10 March, a company of the Chinese Unit 56037 lost one-third of its men as it was holding a hill near Bản Lan against successive Vietnamese assaults.[19] The PLA 163rd Division's advance toward the Kỳ Cùng Bridge on 1 March also met fierce resistance; one Chinese battalion was caught on open ground by heavy weapons firing from Hill 279, where the command post of the VPA 42nd Regiment was situated, and two rock hills near Dong Uyen.[22] While the battle for Lạng Sơn was taking its course, Vietnamese forces also carried out raids against Chinese border towns of Malipo and Ningming, but caused no significant losses.[23]

From the south and the east of Lạng Sơn, it took the PLA 43rd Army two and a half weeks from 17 February to reach the city.[24] Its 127th Division marched from Ba Sơn between border markers 32 and 33 to Highway 1A at Cao Lộc,[25] the itinerary which took the Chinese ten days just to overcome the distance of 5 km from the border to Bản Xâm due to drastic interceptions by the VPA 141st Regiment.[24] To the south of Lạng Sơn, the PLA 129th Division targeted Hill 392, Hill 623, and the township of Lộc Bình after crossing the border at Chi Ma.[25] It took the Chinese eleven days to seize Lộc Bình, which was still 22 km away from Lạng Sơn. Chinese forces kept using mass formation attacks to suppress the strong Vietnamese resistance on these directions.[26]

On 1 March, the PLA 165th Division/55th Army eventually pierced the Vietnamese defense held by the VPA 42nd Regiment at Lam Truong, which was 2 km northwest of Lạng Sơn. Its sister division, the 164th, had also captured the headquarters of the VPA 141st Regiment at Pò Lèo, which was 1.5 km to the northeast.[22] By 2 March, Chinese forces had secured most of the hills around Lạng Sơn, having the city virtually besieged.[23] At Khánh Khê, they encountered elements of the VPA 337th Division, which had been sent to hold off Chinese movement against Lạng Sơn in the area.[27] On 3 March, the Chinese launched their final assault on Lạng Sơn.[23] Contemporarily, the VPA 3rd Division, presumably followed by the 42nd Regiment, had been ordered to withdraw from the city and incorporated into the newly founded 5th Corps, which consisted of the 3rd, 327th, 337th, 338th, and 347th Divisions, for the purpose of future operations.[28] The 12th Regiment, which had been cut off from the rest of the 3rd Division, was assigned to continue defending enclaves along Highway 1B.[19] The Chinese 127th Division advanced across the Kỳ Cùng River at Phiêng Phúc along a line through the hills west of Highway 1B, swiftly overrunning the defense on Mê Mai Hill on its way before capturing the Mai Pha airfield and Hill 391 on the southeast on 4 March.[26][29] On the same day, Hills 332, 317, and 382 fell to two reserve battalions from the 50th Army. The 163rd Division crossed the river between Khủi Khúc and Khòn Pát, penetrating 5 km south of Lạng Sơn to Pac Meng, a movement which had become the furthest advance toward Hanoi direction.[29] On 5 March, the PLA 127th and 129th Divisions entered Lạng Sơn City.[26]

The bridge over the Kỳ Cùng River destroyed after the Chinese occupation of Lạng Sơn

After Lạng Sơn had been occupied, fighting still went on in Lộc Bình and the town of Móng Cái in Quảng Ninh Province. On 5 March, the Chinese government announced the withdrawal of troops from Vietnam. During their withdrawal, Chinese forces had destroyed the bridge south of Lạng Sơn.[30] Vietnamese units in Lạng Sơn, though badly mauled after previous clashes, still continued their fight against Chinese troops. The VPA 327th, 337th, and 338th Divisions, which had been positioned southerly near Chi Lăng to prevent a possible Chinese breakthrough, were finally committed to the battle for a counter-attack. The 337th and 338th pursued and harassed Chinese forces as they were pulling back and returning to Chinese territory across Chi Ma.[27]