If you’ve ever wondered why, decades after the last shots of World War II echoed across Europe and Asia, cities are still grinding to a halt because of ancient bombs, you’re not alone. The ghosts of that global conflict are very much alive—buried beneath our feet, lurking in construction sites, gardens, and even under busy runways. Finding unexploded WWII bombs (UXOs) is not merely some weird piece of historical trivia; it is a very real, true-life danger that can totally turn modern life around at any given time.
That there are so many left today is because of the magnitude of the bombing campaigns. WWII saw hundreds of thousands dropped on cities such as London, Berlin, Tokyo, and hundreds more. They never detonated, due to defective fuses, bad weather, or simple bad luck. It’s estimated that 10% of the bombs that were dropped by the Blitz alone in England did not explode. So much ammo was dumped on Japan by the US that hundreds of thousands of tons of it remain there, particularly in areas such as Okinawa, where perhaps 10,000 tons are buried.
But here’s the catch: these bombs do not become safer with age. In accordance with a study in Royal Society Open Science, World War II explosives such as Amatol—a blend of ammonium nitrate and TNT—become more explosive with age, particularly when contaminated by soil and metal. The longer bombs of this sort linger, the more unstable and sensitive they become.
As two Norwegian bomb specialists learned, aged Amatol is “generally much more shock-sensitive than hitherto presumed.” That is, a shovel in the hands of a construction worker, a backhoe, or hard rain could precipitate an explosion.
A series of high-level bomb scares has occurred in the past few years. In Exeter, England, a 2,200-pound German bomb was discovered on an allotment, leading thousands of residents to be evacuated and resulting in a crater three double-decker buses in length after being exploded in a controlled detonation. As Dr. Todd Gray of the University of Exeter said, “That bomb going off is a reminder of what that generation in 1940s had to go through.” The Ground Self-Defence Force in Japan dealt with more than 2,300 incidents involving almost 38 tons of explosives in a single year, and such as the 23-foot crater at a regional airport in southwest Japan are still making top headlines. 12,400 people were evacuated in Berlin so that experts could remove a Russian bomb found while digging.
Paris’s Gare du Nord train station, which is used by commuters every day, was stopped for half a day when diggers found a 500-kilogram English bomb, stopping 500 trains and inconveniencing 600,000 travelers. Hong Kong has also been forced to evacuate thousands of people after a huge American bomb was found in a business area.
It is a logistical nightmare to excavate and destroy the bombs. Detection technology advances, but the process remains time-consuming and costly. In Japan, for instance, sometimes it takes digging 100 holes just to discover one UXO. Bombs are often buried so deep that it’s the landowners themselves who are supposed to find them and shell out money for them to be destroyed.
In the aftermath of WWII, the haste to rebuild saw bombs paved over or left behind only to surface decades later. The UK Ministry of Defence says it defuses safely about 60 German WWII bombs every year, though many more are handled by private contractors, so it is hard to tell what the true number is.
The effects on communities are deep. Evacuations send hundreds of thousands fleeing, interrupt travel for hundreds of thousands, and render homes unlivable. The psychological damage is real too—particularly in areas like Okinawa, where there is the threat of spontaneous detonation. The unpredictability of these bombs translates to every construction project, every new structure, having a shadow of danger.
It will take another hundred years, maybe, before all the WWII ordnance is removed, according to experts. Until then, the past will keep bursting into the present, one dirty, rusty bomb at a time.