The invasion at Normandy may be the most iconic moment of one of humanity's worst wars. What doesn't often get discussed, however, was the practice and planning that went into the operation. 

If it all went like Exercise Tiger, there might be a good reason why we don't tend to hear about this part of it. 

Source:

Exercise Tiger. Wikipedia. Last accessed on April 13, 2021. https://en.wikipedia.org/wiki/Exercise_Tiger