Victory in the war to protect the southwestern border (in 1979) is of great significance, shattering the conspiracies and acts of invasion into Vietnam by the Pol Pot – Ieng Sary reactionary group, saving Cambodian people from genocide and reviving the country. The war left us many precious lessons about military art, notably the art of force deployment.

After coming to power (4/1975), supported by foreign reactionary forces, the Pol Pot – Ieng Sary group betrayed the revolutionary cause of Cambodian people, undermined the tradition of solidarity and friendship between Cambodian and Vietnamese people, implemented the brutal genocide policy in the country, and irrationally considered Vietnam as an “eternal and No.1 enemy”.

In May 1975, right after the reunification of Vietnam, Pol Pot sent troops to invade our Phu Quoc and Tho Chu islands, killing more than 500 civilians; provoked our border guards; encroached on the borders of Tay Ninh, Kon Tum and Dak Lak provinces. By the end of 1975 and the beginning of 1976, Pol Pot army suddenly penetrated deep into the territory of our country, even more than 10km in some places, such as Sa Thay (Kon Tum), committing many crimes against Vietnamese people. Pol Pot declared that: “Vietanm is the disaster that needs most attention”. Accordingly, they intensified provocative actions, encroached upon our country's border in the areas of Military Regions 5, 7, 9; vigorously prepared for war, built and developed their main army from 07 divisions to 12 fully-equiped and staffed regular divisions together with tens of thousands of local troops, and deployed 41% of their strength, weapons and equipment along the border of our country. Despite all the peaceful diplomatic efforts of Vietnam, Pol Pot still declared: “The conflict between Vietnam and Cambodia is innevitable and irreversible. It can’t be resolved by negotiations but military measures”. On the night of April 30, 1977, taking advantage of our celebration of the second anniversary of the complete liberation of the South and reunification of the country, Pol Pot troops launched attacks on the entire border line of An Giang province, officially starting the war to invade the southwestern border of our country.

Facing the conspiracy and violent aggression of Pol Pot army, on May 23, 1977, the Central Military Commission instructed the southern armed forces to “Resolutely defend the territorial sovereignty of the country; not to tolerate any encroachment of the Cambodian reactionary provocative force into our territory; at the same time, respect Cambodian territorial sovereignty. Find ways to dampen the spirit of provocations,... to crush the plot to divide the three brotherhood countries on the Indochina peninsula”. Under the leadership and direction of the Party, the Central Military Commission, and directly the General Staff, the Southern army and people, with the armed force being the core, fought heroically, ingeniously, creatively to defeat Pol Pot troops, firmly protect the sovereignty and territory of the Fatherland; coordinated with Cambodian revolutionary armed forces and the insurgent movement of Cambodian people to destroy most of the Pol Pot army, gained power, abolished the brutal genocide regime,  established the people's democracy, and restored the country of Cambodia. The war left us many precious lessons on the spirit of revolutionary vigilance; on the defence of the on the spot forces to protect the border; on combining military struggle with political and diplomatic struggle; on combining the military advance from our border with internal insurrection of our neighbour.

The art of force deployment in defence, counter-attack and offensive operations to destroy the enemy, defend the southwestern sovereignty and territory of the country is shown in the following basic issues:

Firstly, adjusting and replacing forces, organising defence in combination with offensive and counterattack operations to push the enemy out of the border, protect the people, the target and the area. At the beginning of the war, because of not anticipating war situations, we were made passive, surprised, and awkwardly coped with the invasion and intrusion of the Khmer Rouge army. But right after that, we promptly instructed the provinces, districts, the armed police (now the Border Guard) to urgently adjust the payroll organisation, supplement the force, and strengthen the defence on the frontier line. In the direction of the 5^th Military Region, we sent the 304^th Battalion of Gia Lai - Kon Tum province and the 17^th Company of Dac To district, combined with the 29^th Regiment, the 1^st Battalion (the 95^th Regiment) of the Military Region stationed in BuPrang - Duc Lap area to increase combat strength; organised defence posts and clusters and formed on the spot mobile detachments which would coordinate with the armed forces of provinces, districts and armed police at border posts to conduct defensive, counterattack, and offensive battles at battalion and regiment levels in order to counterattack, pursue, push the enemy in the area of Sa Thay River, Bu Prang and Truong Tan Buu Posts, ... to the other side of the border and successfully secure and defend the battlefield, protect the area.

After the Resolution of the Central Military Commission on the Southwestern border protection was issued, we urgently adjusted, replaced and stabilised the local army regiments of the provinces, the main divisions of the military regions and deployed part of the ministerial mobile forces to key points of: Ha Tien, Chau Doc, Tay Ninh, etc. The General Staff dispatched the 64^th Regiment (the 320^th Division) and the 10^th Division of the 3^rd Corps to replace the forces of the 7^th Military Region to engage the enemy from the East of Bai Bau to Ta Not, the Cu river confluence. In the focal area of Military Region 9, the General Staff dispatched the 270^th Regiment and the Artillery Company of the 341^st Division to operate in Ha Tien; The 141^st Regiment, the 210^th Artillery Regiment and the 7^th Infantry Division's Armored Company to An Giang. At the same time, it directed junior units to urgently reorganise and consolidate local units, militia and self-defence units in communes, hamlets and villages; coordinate with armed police units; consolidate the system of fortifications, battlefields, barriers, obstacles; regain initiative, prevent and control enemy intrusion, protect people, stabilise the border security and order, get ready to engage the enemy.

Second, coordinate the on-site forces with mobile operational and strategic forces to engage the enemy in all directions. In July 1977, Pol Pot army launched the second major offensive into the provinces of An Giang, Kien Giang, Long An, Dong Thap and advanced towards Tay Ninh, causing many crimes against the Vietnamese people in which more than 1,000 civilians were massacred in Tan Bien and Ben Cau districts (Tay Ninh province). In the condition that we have not organised a solid border defence line, the General Staff decided to use the ministerial main force to repel enemy attacks in many border areas and recapture the occupied areas. Due to the limitations of time, we did not organise offensive or counter-attack campaigns, but operational and strategic mobile forces to conduct attacks and counterattacks in all directions. In particular, we deployed the 4^th Corps to coordinate with the armed forces of 7^th Military Region to attack and destroy the enemy in the direction of Road No. 1; the 10^th Division (3rd Corps) and 5^th Division (7^th Military Region) to attack the enemy in the direction of Xa Mat. These two columns simultaneously launched the first attack to Cambodia, repelling the attacks of the enemy on the direction of Tay Ninh, then retreating to reinforce their forces. Discovering our retreating troops backward, in November 1977, Pol Pot launched a new offensive to capture Tay Ninh town. To cope with this situation, the General Staff deployed the ministerial strategic mobile force (3^rd Corps and 4^th Corps) to coordinate with the main divisions of 7^th Military Region and 9^th Military Region (including 08 divisions) to launch a simultaneous counterattack on the directions of Road No. 7, Road No. 1, Road No. 13, chasing Pol Pot troops out of our border and pursue them deep into Cambodian land, defeating 5 divisions of the enemy and their plan to capture Tay Ninh town. In this period, we mainly used the ministerial strategic mobile force and the divisions of the military regions to conduct independent operations in each direction, attack and capture the targets as in determined plans, similar to clusters of forces in the Ho Chi Minh Campaign.

Thirdly, using concentrated and superior forces, promoting the joint-force synergy, organising simultaneous counterattacks and attacks to end the war. In 1978, although badly damaged, with the support of weapons, equipment and military advice from outside, Pol Pot army still deployed more forces close to our border, carried out attack and encroachment. In particular, at the end of that year, Pol Pot prepared 05 divisions and 04 regiments to attack Tay Ninh with the intention of expanding their invasion to our country. The Politburo and the Central Military Commission urgently approved the General strategic counter-attack and offensive determination - destroying all enemy troops, completing the war to protect the southwestern border of the country; at the same time, supporting the Cambodian revolutionary armed forces to overthrow the Pol Pot genocidal group, take power into the hands of the people. Being aware of our plan, on December 23, 1978, Pol Pot army mobilised 10 out of their 19 divisions which were located along the border to launch attack on the entire border line of our country. Facing that situation, the Ministry of National Defence commanded the Vietnamese Volunteer Army together with the Cambodian revolutionary armed forces to launch the decisisve general counter-attack and offensive across the border. Our combined forces, including the Army, the Air Force, the Navy constantly launched counterattacks and offensives against the enemy with all scales and forms, driving away the Pol Pot army and regaining the entire territorial sovereignty of the country. At the same time, we continued to attack, quickly breaked through the enemy's outer defence line, developed and destroyed 3 main Pol Pot main clusters (each cluster consisted of 04 to 05 divisions) holding No. 1, No. 7, and No. 2 Roads, advanced to Phnom Penh, coordinated with the directions and armed forces of the Cambodian National Solidarity Salvation Front to launch a total attack into and liberated the capital of Phnom Penh. We and the Cambodian revolutionary armed forces destroyed and disintegrated 18 Pol Pot army divisions (in which five divisions were wiped out), destroyed 12,000 enemy troops and captured another 8,800...  liberated 04 million Cambodians, smashed the administration of the Pol Pot Group, and established the Cambodian People's Republic regime.

The war to protect the southwestern border has ended long ago, but valuable lessons on military art, especially the art of force deployment in combat, remain intact for us to study and apply into the future war to protect the Fatherland.

Colonel, MSc. NGUYEN HOANG TUNG