During WWII, Allied bombing runs over occupied Europe had to worry about more than just enemy fighters. At night, German anti-aircraft defense guns lit up the sky and made it look like bombs were going off all around them.
During World War II, the Flak Abwehr Kanone were the first line of defense for many German towns. They could fire from the ground, on rooftops, or from specially made Flak towers. Before planes got too fast for well-placed weapons and had to be shot down with missiles, these cannons were very important for protecting a city from attacks from the air.
The Flak 36 and 8.8-centimeter Flak 41 could fire up to 25 rounds per minute, and the bomb was set to go off when it hit a certain height. That's when the anti-aircraft rounds finally went off. The high explosives inside sent sharp metal pieces in a circle around the missile, destroying any planes that were nearby.
High-explosive Flak rounds also made a deadly plume of black smoke that hung in the air. This allowed attacking Allied planes to know they were close enough to hit the guns on the ground before they could make their bombing runs.
This was done so that Allied bomber crews would not have to deal with German flak fire from the ground. They had to fly their planes higher before lowering them to hit their targets. Of course, this made them easy targets for the enemy, who were very good at shooting down Allied planes.
During World War II, flying a bomber was one of the most dangerous and deadly jobs. One reason for this was flak. The RAF Bomber Command said that 44% of its pilots were killed, more than 8,300 were hurt, and another 9,800 were taken prisoner of war. As of 1943, crews in the U.S. Eighth Air Force were supposed to do 25 combat flights. A lot of them never got past their fifth task.
Flak had a strong psychological effect on bomber pilots as well. Flight doctors discovered that bomber crews had trouble sleeping, bad moods, sudden fits of anger, nausea, weight loss, blurred vision, social withdrawal, trouble focusing, and tremors that felt like Parkinson's after hitting their targets.
When something goes up, it has to come down, just like everything else. That which didn't hit an airplane like a hot knife through butter went the same way as the planes that did hit something: they slammed back down to Earth. Fires from Allied airplanes probably did a lot of damage to people on the ground, but Flak that didn't hit a plane probably didn't hurt people on the ground that much.
For starters, air raids usually made people in a city or area scared, so it makes sense that most civilians were hiding in air raid shelters, where they would be safe from most gravity bombs and other things that fell from the sky during the fight.
Also, most of the high-explosive Flak rounds' material that wasn't meant to explode was made up of light metal pieces and other small pieces. They would be seen as nothing more than trash once they hit the ground. People who were hit by falling objects could get seriously hurt or even lose their lives. This is another reason why air raid wardens and other ground combat troops were given helmets to wear.