In every show and documentary I've seen, the landing craft had one big door on the front that opened as a ramp. Why weren't they designed with doors on the sides or back to provide the soldiers/marines some sort of cover rather than immediately expose them to enemy fire?
The LCI did start out with doors on the side and a ramp going down alongside the bows, but this left them even more exposed than having the ramp in the bow. https://upload.wikimedia.org/wikipedia/commons/2/23/Invasion_Training_in_England_02.jpg
If you put doors at the side or the back, you're going to have infantry jumping out into deep water. This will (a) make them cold, wet and miserable, (b) could make them drown if the water is deep enough, since they're heavily loaded, and (c) it'll take them longer to get to dry ground where they can run and make good time to actual cover. When they're beside the boat, they get cover from one side only, but from the other side, they remain vulnerable, and now for longer. And, finally, the ramp allows more people to get off faster as well as allowing for the transport of vehicles, trailers, artillery pieces et al.
