Using a bamboo ruler... calculate the speed of the enemy aircraft!

We were truly impressed by the story of how he and his comrades in the 367th Anti-Aircraft Artillery Regiment studied the operational patterns of enemy aircraft in order to effectively destroy them during the Dien Bien Phu Campaign.

In early January 1954, the 367th Anti-Aircraft Artillery Regiment received orders to move to a secret assembly point in Tuan Giao to be attached to the 351st Division. This was the Regiment's first time participating in combat against enemy aircraft, so they lacked extensive knowledge of the French Air Force's operational activities. While the unit's officers and soldiers had only received training materials on the operational data of the American F-84 and F-86 jet fighters during the Korean War, they now had access to many types of French aircraft such as the Dakota, B-24, B-26, Hellcat, Bearcat, and Moranne. The Regiment determined that to ensure victory, it was essential to have the operational parameters of the enemy air force.

Taking advantage of the time before the opening shots of the campaign, the Staff of the 367th Anti-Aircraft Artillery Regiment dispatched a reconnaissance team to the summit of Ta Leng Mountain, a high point east of Dien Bien Phu, to study the activities of the enemy air force. Tran Lien (military intelligence and reconnaissance assistant) was assigned as the team leader. When he first enlisted, Tran Lien was assigned to the Air Force Research Department, so he already had some knowledge of air force operations. To the summit of Ta Leng, the team brought several binoculars, a 37mm artillery rangefinder, a stopwatch, and a compass. The most difficult task in studying the activities of the enemy air force was determining the speed of each type of aircraft, their speed when flying in formation, when circling, when diving to attack...

With enemy aircraft operating in the sky, how could they determine their speed using only rudimentary tools? After days and nights of intense thought, team leader Tran Lien came up with the idea of determining aircraft speed using the principle of similar triangles. Tran Lien made a 30cm long bamboo ruler, tying a 50cm long parachute cord to the middle. Each time an enemy aircraft appeared, Tran Lien would bite down on the end of the cord, pull the ruler straight with one hand to eye level, and use a stopwatch with the other. Based on the target's flight time from the beginning to the end of the ruler, combined with the distance measured by the rangefinder, Tran Lien calculated the aircraft's speed. After nearly a month of meticulous and persistent work, the reconnaissance team determined the patterns of speed, time, direction, altitude, turns, dive angle, etc. These were crucial factors for anti-aircraft artillery to identify targets.

On the afternoon of March 13, 1954, the Dien Bien Phu Campaign began, with 24 aggressive attack aircraft swooping down on our starting lines. The anti-aircraft artillery of the 367th Regiment, thanks to thorough preparation and secrecy, unexpectedly and fiercely retaliated. Encountering a dense barrage of fire, the French pilots panicked, flying in all directions, dropping bombs indiscriminately, and fleeing. However, we did not destroy any aircraft in this battle. During the debriefing session on the night of March 13, the unit determined that the cause was the soldiers' lack of composure, the officers' failure to choose the right time to fire, and a lack of focused fire...

At 8:00 a.m. the following day, Company 815, Battalion 383, 367th Anti-Aircraft Artillery Regiment shot down a Moranne reconnaissance aircraft on the spot. This was the first French aircraft shot down by 37mm anti-aircraft artillery since the start of the campaign. At the end of the first phase of the Dien Bien Phu Campaign, the 367th Anti-Aircraft Artillery Regiment shot down 14 aircraft of various types and damaged 25 others. The Campaign Command commended the "heroic young anti-aircraft artillery troops, who achieved a glorious victory in their first battle."

Text and photos: SON BINH

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