the weather and where they landed but the fact that they could bring so much armament so quickly, so much material so quickly into those beaches at mulberry harbor, it's a remarkable engineering feat, quite frankly, isn't it. >> reporter: that's right. there is the question of the engineering capability that they needed to have, the communications capability that they needed to have and on the day, a huge proportion of their communications capability was simply lost. so coordinating many different forces that came from many countries that had had for the couple of years before the landing took place to coordinate what was an incredible -- >> and it looks like our ability to communicate was also lost but it does paint an accurate picture of the impenetratable wall that they were attacking there, five beaches, the key to the allied invasion. >> president trump arriving any moment. he's arrived right there.