Were there any casualties in WW2 from unexploded WW1 bombs?

Effect? No. Unexploded Ordnance from both World Wars continues to be a problem, periodically encountered in any number of situations such as farming, excavation, or construction, and requiring expert disposal, and in some cases causing death or injury, and while we can quite safely assume that it likewise was something encountered at points when the battles of the Second World War traversed the landscape of the First. But to say that such encounters had any effect, in a meaningful sense, on the course of the war is quite unsupportable as there isn’t evidence to suggest it.

As you might expect, there is a lot of literature on unexploded ordnance out there, but it focuses on a peacetime context. A soldier digging a fox hole and encountering an artillery shell that blows him up might be ironic, especially if it was from his own country 25 years before but it doesn’t feel unexpected and tragic in the same way that a farmer being blown to kingdom come when his plow encounters a landmine, a fate which happened far too often, 36 French farmers dying that way in 1991 alone!

The sheer volume can’t be understated here. Estimates are hard to pin down, but can be roughly calculated at least, and are as high as 400 million unexploded shells from the Western Front still. The Somme battlefield alone was turning up around 90 tons of ordnance a year as late as the 1990s, while Ypres more than double.

Moving back to the immediate years after the war the danger being recognized, many believed the land would never be reclaimed. It was, but at a cost, and a number of serious accidents happened during the leveling and clearing of land to return to farmland. Plenty remained to be unearthed later as the Allied and Axis forces traversed that land again, as the record up to the modern-day suggests. But we again need to return to effect.

It is easy to say that it is likely such encounters occurred, but another matter placing any import on them. After all, the most likely situations where still volatile ordnance would be triggered are cases where the impact would be most mitigated, such as a World War II shell impacting near one of its predecessors. The latter might explode and amplify, but there is already a shell blowing up either way!

Unexploded ordnance discovered in a more controlled environment wouldn’t be all that different, in practical terms, than more recent vintage, which the military was already prepared to deal with anyways, with bomb disposal falling under the purview of the engineers in the case of the US Army, and soldiers generally being trained in ‘bomb reconnaissance’, as was termed the process of recognizing and reporting unexploded ordnance for proper handling and disposal.

Trained by the British, who already had a few years experience, although it was often hurried and brief, in any case, it would be their job to handle Allied, enemy, and unidentified ordnance that needed to be safely removed or destroyed. It was a dangerous job, with 111 killed or wounded out of the 972 American men detailed to the duty in Western Europe. Nothing to point if any were specifically World War I vintage that they discovered, but in any case, it certainly points to the duty being no joke, and unexploded ordnance something requiring respect and care.

To be sure, none of this gets to the heart of the question. To return to the starting point, any cases of this happening simply lacked effect. Scanning through a ton of books that might be mentioned such a phenomenon resulted in nothing. We absolutely cannot say with certainty no accounts exist out there, but finding them would likely be luck more than anything else, we suspect (“Unexploded ordnance World War I in World War II” is not an effective search term in Google scholar, let me tell ya’) but hopefully, at least, this provides some context to the nature and extent of unexploded ordnance from World War I, as well as the context in which they might be encountered, and how ordnance more generally might be handled.

We’ll close out with an anecdote that doesn’t quite fit the precise topic, but only because it goes too far back in time! During World War II, Fort Macon was reoccupied by the Army for Coastal protection, and a group of soldiers there decided to use a pair of cannonballs as andirons in their fireplace.

Except one of them wasn’t a solid shot, but a packed, and still volatile shell. Supposedly, a cartoon in the newspaper about the incident related that “Confederate Shell Kills Two Yankee Soldiers 80 Years After It Was Fired”. The moral of the story, certainly, is to assume any old ammunition you find is still active and be safe.