One, two, three… 10, 11, 12… I kept counting. I lost count of the number of water-filled B-52 bomb craters I could see.

Fifty years ago, on August 15, after pressure from the US Congress, then-President Richard Nixon agreed to end all bombing of Cambodia. The bombardment of neighbouring Laos had ended a few months earlier.

In October 2006, a macabre competition developed. Scholars at Yale University reviewing wartime US Air Force archives revealed that Cambodia had been attacked even more extensively than originally thought. From bases in Thailand and Guam, B-52 Stratofortress’s as well as smaller aircraft flew more than 230,000 sorties dropping 2,756,941 tonnes of deadly explosives on 113,716 targets in Cambodia.

Previously, Laos had claimed the dubious distinction of “most-bombed nation”. US planes rained down 2,093,100 tonnes there. Those numbers, of course, must be compared with the tonnes of all kinds of air-delivered explosives and incendiaries striking North and South Vietnam during 20 years of war – a number estimated at more than 5 million.

The air raids began against Laos in 1964 and Cambodia in 1965, at a time both were technically “neutral” in the war next door. Bombing sharply escalated in 1969-70 and continued until 1973.

In the early stages, both Presidents Johnson and Nixon carried the campaigns out “secretly”. While clearly not a secret to those being attacked, both US administrations denied information to Congress and the media and claimed the attacks were on targets in Vietnam.

The deadliest single B-52 strike in Cambodia occurred only a week before the bombing halt. In what was described at the time as a “targeting accident”, 20 tonnes of explosives were dropped on the Mekong River town of Neak Luong, killing or critically wounding 405 civilians.

Mistakes came as no surprise to the Yale data analysts. The intent, of course, was to cripple Communist forces to preserve US allies – the governments of Cambodia in Phnom Penh and South Vietnam in Saigon.

In the race to bomb as much as possible in the final weeks, the US Air Force found itself with too many assets in Thailand and too few targets in Cambodia. The Yale study found that 10 percent of all raids were indiscriminate, designated in the official records as “target unknown”.

The Americans concentrated much of their firepower on relatively underpopulated areas of Cambodia and Laos, which were being used as staging areas for North Vietnamese forces.

No definitive accounting of those killed – military or civilian – is available but the Yale scholars put the civilian casualties at a minimum of 150,000 dead over eight years in Cambodia. In Laos, perhaps half that.

The US munitions, dropped often at night from 32,000 feet, accomplished three things. They delayed by perhaps two years the victories of the North Vietnamese and the Khmer Rouge. They drove many civilians to support the Communists.  And most enduringly, the bombing has continued to kill people for the 50 years that have passed since the air assaults ended.

Two types of ordnance were most often used. The 750-pound M117 Iron bomb caused many of those craters I saw. Last used in Operation Desert Storm in Iraq in 1991, the M117 has been retired from use.

Arguably more deadly then and in the long term, were the CBU-58 cluster-type munitions that the US still stockpiles today.

The Lao and Khmer people called them “bombies”.

Then and now, a single warhead can contain 500 or more small bomblets. What the military calls “submunitions” average about six inches (15cm) long and weigh under four pounds (1.8kg). They burst from their warheads and fall in clusters over wide areas. The horrific post-war danger is that the bombies have a high dud rate. Up to 40 percent of the munitions fail to explode. It’s estimated somewhere between 9 and 27 million submunitions in Indochina remain unexploded today.

The populations of Cambodia and Laos grew significantly as peace prevailed and post-war recovery gained slow progress in the early 2000s. Looking for land to farm, people began moving into the regions most bombed.

The number of accidental deaths soared into the tens of thousands as more civilians began to discover the deadly unexploded ordnance (UXOs).

Since 1995, from his base in Hanoi, US Army veteran Chuck Searcy has been working on efforts, mainly in Quang Tri, Vietnam, to eradicate UXOs. “Across the region”, Searcy told me, “the most tragic cases occur when children pick up 50-year-old bomblets, use them as toys, and lose life or limbs”.

Searcy says he is now involved in primary school education projects to ensure that “children know what bomblets look like and know who to call if they find anything”.

The 2010 Convention on Cluster Munitions signed by 123 nations was supposed to prohibit the use, development, acquisition, stockpiling or transferal of cluster munitions. The biggest manufacturers, Russia and the US, as well as other countries like China and Ukraine, however, refused to sign the convention.

Whether US- or Russian-sourced, cluster bombs have been used since 2010 in Afghanistan, Libya, Sudan, Yemen and Syria. And that is but a partial listing.

When US President Joe Biden approved the transfer of cluster munitions to Ukraine last month, he described it as a “very difficult decision” but that “it was needed”.

The Ukrainians say the munitions will be highly effective against infantry, artillery and truck convoys. Yet, it is probably not what is actually needed now but rather what is available. Cluster weapon stockpiles are there. Stocks of other weapons are low, depleted by the supply to Ukraine to fight Russian aggression.

A Pentagon announcement says that Ukraine will receive artillery-delivered cluster munitions, indicating the US will not provide air-delivered cluster bombs. Still, the provision of these weapons will no doubt encourage the Russians to use more of their cluster bombs in an escalation of airstrikes that have already hit civilian-occupied Ukrainian apartment buildings.

Russia and Ukraine are focused on the immediate battles and the inches of territory they can occupy or free, respectively. But history tells us that the continued proliferation of these munitions may well leave an impact lasting long after the current war is over.

The governments giving and using “bombies” are setting up the next generation for unnecessary deaths. At a minimum, there will need to be a dangerous munitions cleanup when the war is over.

The same governments supplying Ukraine with these weapons will need to help it then, again.

The views expressed in this article are the author’s own and do not necessarily reflect Al Jazeera’s editorial stance.