Answer:
As troops landed on the beaches of Normandy they came under fire from Axis forces. Soldiers had to get past many obstacles while being fired at by heavy weaponry. Allied forces attacked during low tide but still had to deal with the many obstacles. Many soldiers died due to the defensive advantage that the Axis forces had. Some ships were destroyed before they even reached the beach and many vehicles and soldiers were blocked and pinned down due to a combination of fire power and the well placed obstacles of the Axis forces. Troops would have to walk across the long beach and then climb over walls and up cliffs to reach bunkers.
Example of some of the many Axis obstacles used on Normandy Beach:
Hemmbalken were wooden stakes in the ground with mines placed on top of them to destroy landing craft. Czech Hedgehogs were metal structures that were used to block vehicles and infantry. Belgian Gates were metal frames placed on roads and on the beach to block tanks. Ramps were slanted wooden logs with mines placed on them to destroy landing craft. Sea walls were walls used to block infantry from getting too close to the bunkers and had a reinforcing layer of barbed wire on top and behind them. Barbed wire was a curly metal wire with spikes on them to block infantry.