Residents got a first-hand feel for the horrors of World War II when a bomb from that time exploded in a barley field in Ahlbach, Germany. The June 23, 2019 explosion left a gigantic crater. While the detonation was a surprise, it’s happened before and will happen again. There are still unexploded bombs in unexpected places all across Europe. They’re leftover from the years between 1940 and 1945 when the Allies dropped 2.7 million tons of these bombs in an attempt to destroy specific German or German-occupied locales. History and science combine to explain how this bomb came to be and why it went off 75 years after it missed its target.

World War II bomb ingredients

First, the history: The Allied forces did not plan to ever blow up a barley field in the 21st century. Their target three-quarters of a century ago was probably facilities and resources critical to the German war effort. Limberg Airfield was in the vicinity, for example. Built by Luftwaffe in 1944, it was used by the Germans for a year and then captured by American forces in late March 1945. The USAAF then used the facility as an airfield and for wartime radio broadcast. Until the end of the war, it also served as a casualty evacuation hub.

This unexploded WW2-era bomb may also have been intended to demolish a nearby railroad junction critical to the German forces. Unlike the precise hypersonic missiles of current arms races, aerial bombs could miss their mark literally by miles. The bomb that left a 14-foot deep crater on impact was most likely one of the M43, AN-M43 or AN-M64 bombs considered “all-purpose” during WW2. They weighed 500 pounds and a single one could take out an entire steel railway bridge, concrete dock, or medium-sized building.

The Limberg-area bomb was most likely detonated far below ground since the crater it left was 33 feet across and 14 feet deep. This makes sense if you understand how these aerial bombs did their damage. Weapons of mass destruction, this series had the capability to blast intact through a few stories of a high-rise building. When they reached the point where they could do the most damage, that’s when they’d blow up. Many of the bombs dropped during the war missed their targets by literal miles. This particular bomb probably whizzed far below the soil the same way it would have sliced through a tall building.

Why now?

The bomb that went off more than seven decades after it was dropped in the German countryside carried around 280 pounds of TNT, yet its casing was just a third of an inch thick. The people close to the early Sunday morning explosion heard it, and some felt the reverberations, but no one actually witnessed the sight.

As for why the bomb waited so long to explode, modern-day explosive ordnance demolition teams say that’s the result of a decomposing detonation device. Back in the day, many of these bombs had chemical-based fuses that allowed a delayed reaction between impact and explosion. If the detonator did not go off for whatever reason, the bomb would lay in an unexploded state with still-active TNT.

While thousands of these unexploded bombs were eventually made safe and removed after World War II, many were not. This same type of explosion could happen in literally thousands of other places across post-war Europe. According to one bomb disposal expert who spoke to the Smithsonian’s Air and Space, “there will still be bombs 200 years from now. It’s become increasingly difficult. At this point, we dealt with all the open spaces. But now it’s the houses, the factories.”