The things we’ve managed to create during times of war have always been somewhat over-the-top to achieve the most insane of weapons, and back in the 1930’s when World War I was still on everyone’s mind they developed a massive plane known as the Kalinin K-7.
This plane was designed for civilian *and* military usage, but the later military-only variation which came out just 10 years before the Boeing B-17 was something you’d expect to see only in movies. This Flying Fortress had a whopping 12 gunner positions with an electric cart running the tail booms to transport gunners quickly to two machine guns in the tail in case it was ever needed. On top of that this monster could carry a whopping 16 tons of heavy explosives!
As you can see in the video the plane never was designed to function with jet engines, as at the time those hadn’t yet existed, so the designers made due with six rather small propeller engines utilizing twenty engines – which ended up being a VERY large problem. Even still, this is by far and large the biggest propeller plane to ever have existed, but after a several successful test flights the plane crashed in 1933 which killed 15 people and any further look into building a new one.