Have you ever watched any WW2 movie or documentary and thought to yourself, what those metal crosses on the beaches used for?
During World War II, both the Nazi forces and the allies tried any and every possible solution to make their opponents lives that much more difficult, Some of their inventions were incredibly complicated and highly technological, while others were rather simple, cheap, easily made and effective too.
Those odd-looking metal crosses you saw on beaches in those films and documentaries were invented by the Czech Republic, and quite simply called Czech Hedgehogs.
The Hedgehogs were made out of cast iron and were used as a cheaper alternative to building a large wall to protect beaches from tanks. Hundreds of thousands were laid down on beaches to prevent tanks from invading and military boats from approaching the shore when the tide was high.
If a tank were to try and ram a hedgehog, it would catastrophically damage itself. The hedgehogs proved to be incredibly useful and effective during both World Wars.
Take a look at the video below by YouTube channel, Today I Found Out, on What Were Those Weird Metal Things on the Beaches During the Normandy Invasion?