Imagine searchlights at war, and you might picture troops scanning for enemy planes in Europe during World War II. But for the U.S. Army, the Vietnam War was the last chance for its increasingly obsolete, high-powered lamps to shine.
Between 1965 and 1967, the Army deployed four searchlight batteries to South Vietnam. Technically artillery units, these soldiers spent most of their time keeping watch over friendly base camps, freeing up the infantry for other missions.
“As is generally known, one of the principal differences between counterinsurgency and conventional wars is that the majority of insurgent operations are conducted under the cover of darkness,” Army Brig. Gen. John Boles Jr., the director of the Pentagon’s Joint Research and Test Activity, explained in the introduction to a 1965 report on the potential utility of the lights. “Therefore, illumination of the battle area has become vital.”
Despite soldering on throughout the conflict, the searchlights eventually fell victim to ever improving night-vision gear.
By the time Battery B, 29th Artillery arrived at Qui Nhon in 1965, the searchlight was already showing its age as a weapon of war. American anti-aircraft gunners had already given up the lamps in favor of far more powerful radars.
Army artillerists were no stranger to the radar game either. The ground combat branch shipped AN/MPQ-4 units to southeast Asia to look for enemy mortars and larger AN/TPS-25s to scan the battlefield in general.
Compared with these sleek-looking dishes and radomes, the 30-inch carbon arc lamps looked positively … archaic. An early 19-century technology predating the incandescent light bulbs most people are familiar with, a carbon arc design produces an intense light by shooting a bolt of electricity between two electrodes.
A year before the first searchlight soldiers arrived in Vietnam, Army leaders had even recommended shutting down the last two active searchlight platoons. Instead, the ground combat branch decided that the World War II-era equipment had distinct advantages for fighting guerrillas and increased the size of the light units fivefold.
Most importantly, the gear was easy and cheap to use compared to the alternatives. Bad weather, fires, smoke and other environmental hazards could hamper planes flying in to drop illumination flares.
Soldiers could also point the beam of light exactly where it would be most useful. Focused to its brightest setting, the lamp could put out 400 million candlepower — far brighter than direct sunlight at noon — onto a target nearly 10,000 yards away. To a lesser degree, troops could brighten up the darkness across a broader area by bouncing the light off low-lying clouds or just shining it into the night sky.
But tests with the South Vietnamese Army showed that the system was far from perfect. Rain, fog and physical obstructions limited the light. Hardly ideal for discreet operations on the move, the arc lamps needed a large and noisy gasoline-powered generator to keep running. And no matter where they were, the big, bright lights offered a huge target for enemy troops.
Nevertheless, American commanders concluded that the searchlight had a place in the war, particularly around outposts, bridges and other facilities.
However, the fighting wasn’t static. Viet Cong guerrillas would often distract attention to one side of a base before throwing their real weight from the other direction.
Combat engineers — commonly referred to as sappers — might try to breach defenses at various locations at once. The Army quickly realized that the heavy lamps were a pain to move into position during these complex attacks.
So two years after deploying to Vietnam, Battery B traded in its 30-inch units for twice as many smaller 23-inch xenon searchlights. Similar to traditional arc lamps, these types shoot electricity between electrodes in a chamber full of ionized xenon gas.
In addition to being simpler and more efficient, the new AN/MSS-3 lights were small enough to fit on a standard M-151 jeep — and were able to put out beams in the visible or infrared spectrum. With special binoculars or telescopes, troops could see enemies without giving away their positions.
The lighter lamps only put out 120 million candlepower. The ability to quickly change positions during a fight easily offset any issue arising from the dimmer light. When Battery B’s sister units — Batteries G, H and I, 29th Artillery — deployed to Vietnam, their soldiers already had the new lamps in hand.
In many cases, Army commanders paired the new trucks with anti-aircraft weapons to protect fire bases. With no threat of enemy air attacks, the ground combat branch turned its 40-millimeter M-42 tracked anti-aircraft vehicles of quadruple .50-caliber M-55 machine gun turrets on enemy guerrillas.
The Viet Cong took notice of the combination. “The employment of automatic weapons and searchlights has proven extremely effective not only in open engagement of the enemy but also a deterrent against enemy attacks,” the commander of 4th Battalion, 60th Artillery — one anti-aircraft unit with the searchlight teams attached to it — noted in one 1968 report.
At various sites, the jeeps conducted their own brand of the Army’s “harassment and interdiction” missions. Usually performed by firing artillery shells at random into predetermined areas , the searchlight teams would instead shine their beams into those locations or nearby villages.
These so-called “H and I” strikes were supposed to keep insurgents on their toes, but often killed innocent civilians or wildlife instead. While non-lethal, the bright lights shining into peoples’ homes in the middle of the night probably didn’t win any hearts and minds.
And despite their new, mobile nature, the lights were still prime targets. “To fully exploit the capabilities of the jeep mounted searchlight, it is necessary to move the light to several alternate positions each night,” officers from 1st Battalion, 44th Artillery reported in 1967.
Not that this necessarily mattered. The AN/MSS-3's infrared feature was already pointing toward a new future.
Early “Starlight scopes” and other night vision gear wasn’t particularly effective at long distances or in especially poor light. But engineers were steadily improving passive systems — those able to amplify existing light rather than needing an invisible light source like an infrared lamp.
In 1969, the Army shipped nine new AN/TVS-3 searchlights to South Vietnam. Three years earlier, the ground combat branch had started working on these 30-inch xenon units as a similarly powerful replacement for the older carbon arc designs.
While the new units were successful, the writing was on the wall. “The 30-inch xenon searchlight be deployed … on a mission-justified basis,” the Army Concept Team in Vietnam evaluators wrote in their final report.
With Vietnamization in full swing and American and other friendly troops starting to pull out of the country, there just wasn’t any point in developing more lamps of any kind. As of 1972, the last of the Army’s searchlight units had packed up and left Southeast Asia.
By the end of the decade, in line with the pre-Vietnam plans, the Army had stood down the batteries entirely. Searchlights continued to be a feature on tanks for some time afterwards, but the Army eventually replaced those devices with night vision and thermal imaging equipment.
While spotlights still have their uses, their time as a battlefield tool has largely passed. For the U.S. Army, its huge searchlights had finally gone out.