Operation Hiep Duc – Dong Duong 1965 launched by our armed forces and people in the battlefield of 5^th Military Region initially destroyed a crucial part of the Saigon puppet and American forces operating in the contiguous area between mountainous area and the coastal plain. The success of this Operation greatly contributed to the progress of our strategic offensive; while affirming a new development of our art of strongpoint encirclement, reinforcement ambush.

In 1965, with the intention of using military power to quickly secure a decisive victory in South Vietnam, the U.S decided to implement the strategy of "Attrition warfare". This is a new dangerous escalation, showing the hawkish nature of the US Imperialist in Vietnam War. To realise this plan, they strengthened military bases of Phu Bai, Da Nang, and Chu Lai, Quy Nhon and Cam Ranh with elite units and advanced military equipment. However, after Operation Plei Me, the enemy troops stationing in 5^th Military Region were isolated, forced to cluster in their bases, sub-sectors and district capitals. To prevent us from attacking, they sent daily combat patrols to the surrounding areas of their bases to intercept our forces. In Hiep Duc – Dong Duong and Que Son, Thang Binh, Tien Phuoc, the enemy deployed several elite units equipped with advanced military equipment supported by security, civil defence and ranger contingents to maintain security for local military bases and the district capital of Hiep Duc (Quang Nam).

On our side, we realised that the enemy in 5^th Military Region battlefield were bewildered and wavering, so if we increased activities to destroy strategic hamlets and attack military bases to neutralise a number of regular units, U.S expeditionary units would directly join the fight, giving us the opportunity to destroy them as well. Our plan was that after concluding operations in mountainous areas, we would step up military activities at areas adjacent to the coastal plain. Therefore, 5^th Military Region Command and Party Committee decided to launch Operation Hiep Duc – Dong Duong to partly destroy enemy main force, step up guerilla activities, form “American-killing belts”, and expand our control in rural area. Under the leadership and direction of the Operation Command and Party Committee, the people and military units of 5^th Military Region managed to complete all the objective set out for the Operation. With 3 phases of operation conducted in a short time, we eliminated an important proportion of the enemy force, and secured initial victory over the US expeditionary force in the contiguous area, gaining strategic advantages on the battlefield; at the same time, this victorious operation affirmed the maturity of our main force’s ability to employ operational art; in which the highlight was the art of point encriclemnt, reinforcement ambushing.

1.Correct target selection to lay siege, destroy and set up ambush against reinforcement. In combat, the correct selection of the area and the target to attack shows the ability to properly assess the enemy situation and the terrain in the area of operation of the commander and his staff. Thanks to this, units participate in the battle are able to demonstrate their full combat potential and forte and exploit the enemy’s weaknesses, causing confusion in their formation and forcing them to react passively. Hiep Duc – Dong Duong was the first operation we concentrated a force with divisional strength to fight against both the US and Saigon puppet troops. In this Operation, the Operation Command conducted evaluation and analysis to correctly determine the enemy fighting methods and tactics, and area of operation in order to identify targets and our own fighting method: encircle and destroy suitable targets and defeat the enemy reinforcement; in which the elimination of enemy reinforcement was the main objective. To ensure the success of the first battle, the Operation Command decided to attack the district capital of Hiep Duc and encircle Viet An outpost as a “provocation”, in order to lure the enemy reinforcement, thus creating favourable condition for our units to eliminate a major enemy force outside of their defensive fortification. This was a right call because Hiep Duc was the outermost area of the enemy defensive line along Route 16, therefore, once Hiep Duc was under attack, the enemy would surely send reinforcements to rescue their units. Viet An was a relatively strong defensive position watching over the junction from Ha Lam to Hiep Duc and Viet An to Tam Ky, if Viet An was lost, the enemy defensive disposition in the area would be divided and they would also lost control over Hiep Duc. These two key targets, while located on our main attack direction, were of utmost importance to the enemy, so if we attacked and encircled them, we would definitely be able to draw the enemy reinforcements and destroy them.

The developments of the Operation had shown that, choosing Hiep Duc as the target for our opening attack was a correct decision by our Operation Command, because after only 1 hour, our force managed to take complete control of this district capital, forcing the enemy to send reinforcements to recapture it. This move by the enemy enabled our units to set up ambushes to destroy the enemy airbourne reinforcements at Son Hill and Tranh Hill. As expected, after 12 days of the siege of Viet An, the enemy deployed a task force to relieve this outpost. This created an opportunity for  us to eliminate most of the enemy 11^th Ranger Battalion. It was the decision to choose Hiep Duc and Viet An as the first targets to attack that “triggered” the enemy’s reaction, forcing them to send airbourne and land reinforcements to rescue these bases, creating opportunities for us to destroy them to complete objective set out by the Operation Command.

2.Flexible employment of fighting methods and tactics. In operational combat, attacking and encircling targets are activities that lead to further situations and trigger chain reactions, forcing the enemy to send reinforcements, this creates opportunities for us to destroy them outside of their defensive fortifications. To effectively encircle and destroy enemy defensive outpost and successfully ambush enemy reinforcements, besides firmly grasping the enemy’s fighting methods, the combat leader must apply different tactics flexibly and creatively for each engagement and terrain. In Operation Hiep Duc – Dong Duong, the Operation Command employed various tactics and fighting methods such as: attack, assault, ambush, manoeuvring assault, wide envelopment, etc, to make the enemy confused, forcing them to react passively and play into our hand.

At the beginning of the Operation, our Command used heavy assault as the tactic to capture Hiep Duc, after that, 90^th Battalion, a 12,7 mm anti-air machine gun, and local military units set up an ambush at Son Hill and Tranh Hill to eliminate enemy airbourne reinforcement attempting to recapture Hiep Duc. Also in this first phase, when our force was not able to intercept enemy helibourne reinforcement at Hoa Que and Hill 230, the Operation Command ordered the entire 1^st Regiment to assault Tranh Hill and the surrounding area. In the second phase, when we were laying siege to Viet An, the enemy deployed a mobile task force to reinforce and relieve this outpost. Knowing the enemy’s intention and their marching formation, we used 70^th Battalion to ambush and completely destroy enemy 11^th Ranger Battalion, the remnant of this task force had to withdraw to Dong Duong and regroup at Ong Trieu Bridge. Seizing this operational opportunity, our Command adjusted our plan from ambush to assault, surprising the enemy and after only 1 hour of combat, we managed to destroy a critical proportion of enemy force including the enemy 5^th Command and take complete control of Dong Duong. In the third phase, we deliberately avoided direct engagements with the enemy and organised envelopments to hit them in their flank and from behind. To this end, our 1^st Regiment conducted manoeuvring assault against the enemy formation en route from Cam Long to Cam Khe, causing heavy casualty to this contingent.

3.Proper force organisation and employment. It can be said that, organising and employing forces to encircle and capture an enemy outpost and ambush their reinforcement is an art, especially when fighting against an enemy with superior number and equipment. In applying this tactic, normally the attacking force is divided into two contingents: one for encircling or capturing enemy position, one for ambushing enemy reinforcement. If the organisation and employment of these contingents are implemented properly, high combat performance is very likely. On the contrary, if we use too many troops for assaulting or encircling enemy position, there will not be enough troops to destroy enemy reinforcement. On the other hand, if we attack or encircle the enemy position with insufficient strength, there will be not enough pressure to force the enemy to send in reinforcement.

In Operation Hiep Duc – Dong Duong, to capture Hiep Duc, the Operation Command used 2 battalions supported by air-defence contingents to attack Son Hill and Hiep Duc administration compound, commando force to attack Tranh Hill and Que Son local units to enegage the enemy at Lon Mountain. Thanks to this correct use of force, after only 1 hour of fighting, we managed to capture the district capital of Hiep Duc. After that, the enemy command sent 2 battalions to recapture this target; to deal with this force, Our Operation Command only used 40^th Battalion, a 12 mm anti-air machine gun company and some minor attachments, therefore we could not destroy a large number of enemy troops. In the second phase of the Operation, learning from the experience of the first phase, the Operation Command used 1 battalion (60^th Battalion) and 03 guerilla platoons to encircle Viet An; 03 battalions (40^th, 70^th, and 90^th Battalion) to deal with enemy reinforcement; we also set up 02 fire support positions Southwest and Northeast of Viet An to suppress the defending enemy and provide air defence for our attacking formation. After only 2 hours of fighting, we completely destroyed enemy 11^th Ranger Battalion attempting to relieve Viet An, the remnant of enemy reinforcement task force had to withdraw to Dong Duong and was later destroyed by 2^nd Divison in the decisive battle of the Operation.

Operation Hiep Duc – Dong Duong caused the initial destruction of the US and Saigon puppet forces in the contiguous area between the mountainous area and the coastal plain, expanding liberated zones and creating developments in our strategic offensive posture in the Southern Battlefield. The success of this operation provided us many invaluable lessons, especially in the art of strongpoint encirclement, reinforcement ambush that needs to be study further and employed in potential future defensive war to protect the Motherland.

Colonel, Dr. BUI DANG LONG, Army Academy