80 years ago, it is the early morning hours of 16 May in England. Supreme Allied Command has begun sequestering select troops, sailors, and airmen. This is done to silo different units so as to contain spread of information. In a few hours time, the select first group of men will begin intensive training on waterproofing weapons, vehicles, and armor for the beach assault. Most of them have gone to bed never having seen plastic in their rural lives. 24 hours from now, they will know how to water-seal grenades, heavy machine guns, medical equipment, rations, and other equipment. None of the assault on the 5 beaches can occur if even 20% of the equipment and weaponry gets water-logged and sinks/jams.
Again, one of 100 things that must go right for Overlord to be successful. One word for you men this time, "Plastics." As fate would have it, the originator of what we know now as 'plastic' (albeit in a different form), Leo Baekeland, dies just ~120 days before D-Day. But his work will allow the Allies to take Ghent, Belgium where Baekeland's family is still based, also in ~120 days time.