“Why is this? Of all the battles in all the wars across the span of human history, why does this day hold such a revered place in our memory? What is it about the struggle that took place... that brings us back to remember year after year after year? Part of it, I think, is the size of the odds that weighed against success. For three centuries, no invader had ever been able to cross the English Channel into Normandy, and it had never been more difficult than in 1944.” - President Obama, 2009 
Today we remember the biggest logistics operation ever attempted... D-Day: June 6, 1944. The operation involved "millions of tons of supplies, thousands of ships, and hundreds of thousands of personnel..."  Key to the operation was "leaked" false intelligence that an invasion would happen at Pas de Calais, France, when it was actually going to occur at Normandy.
Nicknamed Operation Overlord, and over a year in planning, the attack would begin this way: "[An] initial landing force would seize a lodgment, allowing a logistical buildup to follow. Five attacking divisions, each with its own beachhead-code -- named, from west to east, Utah, Omaha, Gold, Juno and Sword -- would seize the bridgehead. A massive paratroop drop by the U.S. 82nd and 101st Airborne divisions west of Utah would prevent counterattack and take German defenses in the rear. Similarly, on the eastern side of Normandy, the British 6th Airborne Division would seize the bridges over the Orne River and the Caen Canal, also blocking counterattack."  The date and time were chosen to correspond with the lowest tide of the month, so the Allies could take best advantage of the space between them and the German defenders on the hills.
Most of the Allied paratroopers dropped in their zones, but the Americans weren't so lucky. The 82nd and 101st were "blown all over the Cotentin Peninsula and Normandy. Luckily, this dispersal helped the invaders. Seeing American paratroops all around them completely confused German commanders in D-Day's first hours."  And that wasn't the only issue the Americans had. As portrayed in many movies, the troops assigned to the Omaha beach area landing were almost completely unsuccessful. "Out of 32 amphibious tanks that were supposed to swim ashore to support the infantry, only five reached the beaches. The rest foundered, and most of their crews drowned. Virtually no first-wave howitzers made it through the roiling surf, either." 
But the Allies did prevail before the day was out, and the initial attackers had cleared the way for the troops behind them. "As the sun set on June 6, the Allies had lodged themselves in western Europe. By the end of the day, they had gotten about 156,000 men ashore by aircraft and ship. In all, eight divisions were ashore. In the west, the Americans had solidly established a beachhead for the VII Corps, into which poured vast numbers of men and mountains of supplies." 
The ProQuest History Vault WWII module, U.S. Documents on Planning, Operations, Intelligence, Axis War Crimes, and Refugees, has much more information on D-Day and other battles of the Second World War. This module presents several major collections of records on World War II, including Franklin D. Roosevelt’s Map Room Files, Records of the Joint Chiefs of Staff, Records of the War Department Operations Division, U.S. Navy Action and Operational Reports, Records of the Office of War Information, Papers of the War Refugee Board, and Top Secret Studies on U.S. Communications Intelligence During World War II. These records are supplemented with smaller collections documenting U.S. planning and participation in World War II.
Click here to read the LibGuide on this module, and read more about D-Day on the LibGuide page ("Operation Overlord ([invasion of Normandy])" under the heading Military Operations-European Theater).
Click here to check out the History Vault module U.S. Military Intelligence Reports, 1911-1944. You can also look over our World Conflicts page and sign up for free trials.
 Obama, B. H. (2009, Jun 06). Remarks on the 65th anniversary of D-day in normandy, france. Daily Compilation of Presidential Documents, 1-4.
 McCammack, J. (2008, 06). The logistical triumph of operation overlord. All Hands, 40.
 Williamson, M. 2002, D-day: Operation overlord. Military History, 58-58+.
[Top photo from Barnes, Fred. The Weekly Standard 9.41 (Jul 5-Jul 12, 2004): 25-27. Photo copyright June 2014, Hulton-Deutsch Collection/CORBIS.]
[Thumbnail photo copyright June 2014. From Anderson, S., & Eschle, L. (2003, 06). 82nd airborne trooper from sicily to the siegfried line. Military History, 20, 50-57.]