The major purpose of airborne forces on D-Day was to protect the flanks of the invasion force by securing choke points, disrupting enemy forces and defending against counter attacks. This image shows the insertion of airborne forces, look for the blue aircraft silhouettes at either end of the invasion beaches. On the West of the map the southern-most silhouette has a line to a square with a cross in it, two Xs and the number 101. This is the map symbol for 101st Airborne Division and if you look closely the dotted line ends in three arrows to show the planned landing grounds south of the Carentan Estuary around the town of Carentan. This is an important location as it marks the boundary between the US VII Corps landing on Utah beach and US V Corps landing on Omaha beach. The corps boundary is annotated using a line intersected with XXX and you can see that it runs through the centre of the Carentan Estuary.

The Corps boundary is important as this is a potential weak spot which could be exploited by the Germans. The hierarchical nature of military organisations means that units instinctively report up their chain of command rather than across to other units. At a corps boundary this means that enemy action sighted by one corps is likely to be reported all the way up to the Army Headquarters (US First Army in this case) before it is reported down to the other corps. This delay in communication can be exploited by the enemy and German doctrine specifically encouraged commanders to look for command boundaries in order to break through and encircle enemy forces. This is what happened during the Fall of France in May 1940 when von Rundstadt’s Army Group A broke through at Sedan on the boundary between the French 2^nd and 9^th Armies. Note that the higher the boundary level (platoon < company < battalion < brigade < division < corps < army < army group) the more command levels information has to traverse and so the longer the delay. A corps boundary is therefore a serious weak point.

So what does this mean for your Grandfather? As a lightly equipped paratrooper he would have jumped into darkness shortly after midnight on 6 June 1944 aware that he had to find, hold and maintain a defensive position in enemy territory and set about disrupting enemy lines of communication until he was relieved by forces advancing from the invasion beaches. He would have been aware that if this task failed then the enemy could drive a wedge through the centre of First Army and then defeat the US Corps in detail leading to the collapse of the Western end of the Allied beachhead. The good news is that with allied air and naval superiority he could rely on overwhelming fire support.

In reality 101^st Airborne had mixed luck. Some elements arrived on time in good order, whereas others were ravaged by anti-aircraft fire or blown off course by wind. The Division’s artillery regiment lost all bar one of its guns. Successful missions including securing exit routes form Utah beach to be used by the 4^th Infantry Division; destroying the Saint-Martin-de-Varreville coastal battery; and capturing or destroying a number of bridges.

What does this mean for you? Now that you know the unit he was in you can do your own research on what happened. The /r/AskHistorians reading list recommends Overlord, D-Day, and the Battle for Normandy by Max Hastings, but for the layman interested in US airborne forces in particular I would recommend World War 2 Soldier Stories Part VIII: True Airborne Stories of the US Paratroopers by Ryan Jenkins. Band of Brothers by Stephen E. Ambrose is the most famous book on the subject, thanks to the TV series, but it focuses on one company of the 101^st and so may only be representative of what your Grandfather did than a record of what he actually did. Unless of course he was in Easy Company of the 506^th Regiment in which case go and read the book now!

Outside of literature you can contact the 101^st Airborne Division Association with his service details and see what information they have from unit diaries or official histories. Once you find out what regiment/company he was in then there is a good chance you will be able to follow his activities for the remainder of the war.

Do you know which regiment or company he was in?