When a missile strike slammed into a residential complex in Yemen's capital Sanaa on May 1, it killed at least 20 civilians and made wreckage of their homes.

The next day, the remnants of family life cut short were scattered among the rubble — scraps of bedding, children's toys, and dazed relatives wondering how and why they had been the ones to survive.

But there was also something else — a flat scrap of metal that provided a clue as to the origins of the blast. It was the tailfin of a GBU-24 Paveway-III Enhanced laser-guided bomb, manufactured in the United States by the Massachusetts-based company Raytheon.

The missile was identified by Mark Hiznay, an armaments expert at the New York-based monitoring organization Human Rights Watch (HRW), from footage featured in the VICE News film Yemen at War: Sanaa Under Attack, which is released today.

It is the first time that an identifiable munition used in Yemen has been linked to specific civilian deaths since airstrikes by a Saudi Arabia-led coalition begun in late March.

'We are bracing for famine, the state disintegrating, and full-blown civil war'

Standing in the wreckage of his home, Jamal Abdel Wahid described how his 18-year-old wife, two months pregnant, was crushed by a concrete slab caved in by the bombing. The blood of Wahid's dead wife and injured children was smeared on a nearby wall and basin.

More than 1,800 people are thought to have been killed in the conflict, including at least 800 civilians. More than half a million people are internally displaced.

The bombing campaign was launched by Saudi Arabia with the objective of defeating Houthi rebels, allegedly backed by Iran, who swept into the capital last year. The Houthis, loyal to former president Ali Abdullah Saleh, are fighting forces backing exiled current President Abd Rabbuh Mansour Hadi, and now control much of Yemen's populated area.

The coalition operation has so far failed to restore Hadi but has brought about a humanitarian crisis. "We are bracing for famine, the state disintegrating, and full-blown civil war," Hisham Omeisy, a Sanaa-based political analyst, told VICE News.

At the outset of the airstrikes, Washington authorized logistical and intelligence support to the coalition led by Saudi Arabia, the country which is one of its most important global allies and the world's largest importer of military technology, much of it from major US companies such as Raytheon.

In April, intelligence cooperation expanded. An official told Reuters that one of the objectives of the cooperation was to avoid strikes on civilian areas.

Britain's Foreign Secretary also promised the UK's support, "in every practical way short of engaging in combat."

Yet prominent civilian targets have repeatedly been hit, reportedly including an Oxfam warehouse, a dairy factory, and a refugee camp.

US-supplied cluster bombs were dropped on the Houthi stronghold of Saada during late April, according to research by HRW, although the organization was unable to identify specific casualties at the time.

Cluster munitions, which scatter many small bombs over a wide area, are banned by more than 90 countries because they tend to leave behind unexploded ordnance which can kill and injure civilians for years to come.

'It's not hard to see how witnessing bombs labelled 'made in America' dropping on Saada had a radicalizing effect'

American bombs have fallen on Yemen since long before the current campaign.

In a series of wars against the Houthis between 2004 and 2010 the Yemeni and Saudi Armed Forces, both backed by the US, bombarded Saada province, killing thousands.

When VICE News journalist Ben Anderson visited the area in early 2014 he found cluster bomb casings bearing US imprints and heard reports of ongoing civilian casualties, as children and farmers stumbled across the unexploded ordnance.

"Anti-Americanism has always been a key part of Houthi ideology," Adam Baron, a visiting fellow at the European Council on Foreign Relations, told VICE News. "That being said, it's not hard to see how witnessing bombs labelled 'made in America' dropping on Saada had a radicalizing effect — just as was the case in the southern provinces where similar bombs occasionally killed civilians while targeting al Qaeda fighters there."

As well as causing resentment and prompting a humanitarian crisis, the bombardment seems far from achieving its objectives.

Although the conflict is often described as a proxy war pitting agents of Shia Iran against those of Sunni Saudi Arabia, the more complicated reality is that Houthi grievances go back decades and are rooted in essentially domestic concerns, rather than a sectarian agenda or Iran's regional ambitions.

A protracted war is unlikely to finally defeat the movement, but has the potential to deepen tensions latent in Yemeni society, with long-term implications.