On March 15, 1945, the first of more than 1,300 bombers crossed the Channel coast north of Amsterdam at an altitude of almost five miles. They flew on into Germany, and around 2:40 p.m., 10 miles northwest of Berlin, the city of Oranienburg appeared beneath them. Sitting in the lead plane, the bombardier stared through his bombsight into the haze below. Five bombs tumbled into the sky.

Between 1940 and 1945, U.S. and British air forces dropped 2.7 million tons of bombs on Europe, half of them on Germany. By the time the Nazi government surrendered, in May 1945, the industrial infrastructure of the Third Reich — railheads, arms factories, and oil refineries — had been crippled, and dozens of cities across Germany had been reduced to moonscapes of cinder and ash.

Under Allied occupation, reconstruction began almost immediately. Yet as many as 10 percent of the bombs dropped by Allied aircraft had failed to explode, and as East and West Germany rose from the ruins of the Reich, thousands of tons of unexploded airborne ordnance lay beneath them. In both East and West, responsibility for defusing these bombs — and for removing the innumerable hand grenades, bullets, and mortar and artillery shells left behind — fell to police bomb-disposal technicians and firefighters, the KMBD.

Even now, 70 years later, more than 2,000 tons of unexploded munitions are uncovered on German soil every year. Before any construction project begins in Germany, the ground must be certified as cleared of unexploded ordnance. Last May, some 20,000 people were evacuated from an area of Cologne while authorities removed a 1-ton bomb that had been discovered during construction work. In November 2013, another 20,000 people in Dortmund were cleared out while experts defused a 4,000-pound "blockbuster" — a bomb that could destroy most of a city block. In 2011, 45,000 people were forced to leave their homes — the largest evacuation in Germany since World War II — when a drought revealed a similar device lying on the bed of the Rhine in the middle of Koblenz.