One of the greatest speeches ever given, in my humble opinion, commemorating the D-Day invasion, was that made by Ronald Reagan on this day in 1984.
Go there and read it all. An excerpt:
We're here to mark that day in history when the Allied armies joined in battle to reclaim this continent to liberty. For four long years, much of Europe had been under a terrible shadow. Free nations had fallen, Jews cried out in the camps, millions cried out for liberation. Europe was enslaved, and the world prayed for its rescue. Here, in Normandy, the rescue began. Here, the Allies stood and fought against tyranny, in a giant undertaking unparalleled in human history.