In June 1966 the USMC were conducting Operation Jay, a sweep and clear operation hunting for VC forces in Quang Dien District. This is about 13 miles north of the famous city of Hue, that would reach the headlines during the Tet Offensive. The forces deployed included two battalions of marines and an artillery battalion. Towards the end of June the operation was being wound up with only a single battalion staying in the area, while the other forces were withdrawn.
It took them an hour to reach the 0 Lau River, passing a column of USMC heading to Hue about five km from the city. Shortly afterwards the VMC convoy entered a series of rolling hills that was open to the west. To the east was a railway that ran parallel to the road, and was cut into the hillside. As the column reached the middle of the 3km stretch of open ground the enemy struck.
Under the pounding the VMC deployed in an orderly fashion from their trucks and took up what little cover there was and began to return fire. Looking west there was a thin stand of trees which could be seen through, beyond this they could make out the black blasts and muzzle flashes of enemy weapons. Then they could see the VC starting to prepare an assault. The VMC commander immediately realised that the roadway had almost no cover and ordered his men to fall-back to the railway.
USMC advisor's with the VMC battalion luckily had their own radios, and managed to contact a US Army observer plane nearby. The USMC artillery which had been listening in to the same net as the US army plane immediately offered fire support, which was gratefully accepted. The first salvo of shells impacted at 0846. Then the thunder began. Another observer plane arrived overhead, this one belonged to the USMC and on-board was a specialist Forward Air Controller. The FAC was in contact with F-4 Phantoms that were arriving in the area and he began to direct these strikes on the enemy.
The Ontos had a reputation amongst the VC. It's bullet proof nature with horrific fire-power and unsurpassed mobility meant that it was rather feared. For example the 106mm recoilless rifle had a beehive round, each of these had 10000 metal flechettes inside it. So an Ontos could blanket an area with such fire-power that an reporter writing about the Battle Khe San said of the Ontos "[...] enough flechette ammunition to pin the entire North Vietnamese Army to the face of Co Roc Mountain".
In this particular case the Ontos platoon managed to get into position flanking the ambush. With airstrikes and artillery raining down, reinforcements arriving from both south and north, including a platoon of the feared Ontos, the VC broke and ran. The ones at the railway cutting had plenty of cover. However the force on the open ground to the west of the road lacked any such cover for their flight. One platoon waiting until it thought it was all clear left their position at speed hoping to get to more cover before another air strike or artillery could be directed at them. They'd forgotten about the Ontos’s. The Ontos platoon fired one round from each gun, and swept the VC platoon from existence.
Bundle of Beehive flechettes. Multiple of these would have been stacked inside the cone of the round.
The fight was all but over, with the forces west of the road being cut off by air mobile troops and surrounded. It cost the VC battalion 185 killed and most of its crew served weapons. The VMC had lost 42 dead.
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