1944 June 5th. Allies bomb German batteries.

On March 23, 1942 Führer Directive Number 40 called for the official creation of the Atlantic Wall. After the St. Nazaire Raid, on April 13, 1942  Hitler ordered naval and submarine bases to be heavily defended. Fortifications remained concentrated around ports until late in 1943 when defences were increased in other areas. 
• Organisation Todt, which had designed the Siegfried Line (Westwall) along the Franco-German border, was the chief engineering group responsible for the design and construction of the wall's major fortifications. Thousands of forced labourers were impressed to construct these permanent fortifications along the Dutch, Belgian and French coasts facing the English Channel.
  Early in 1944, Field Marshal Erwin Rommel was assigned to improve the Wall's defences. Rommel believed the existing coastal fortifications were entirely inadequate and he immediately began strengthening them. Under his direction, a string of reinforced concrete pillboxes was built along the beaches, or sometimes slightly inland, to house machine guns, antitank guns and light artillery. Mines and antitank obstacles were planted on the beaches themselves and underwater obstacles and mines were placed in waters just off shore. The intent was to destroy the Allied landing craft before they could unload.
  By the time of the invasion, the Germans had laid almost six million mines in northern France. More gun emplacements and minefields extended inland, along roads leading away from the beaches. In likely landing spots for gliders and parachutists, the Germans emplaced slanted poles with sharpened tops, which the troops -called ("Rommel's asparagus"). Low-lying river and estuarine areas were permanently flooded, as well.
  Rommel firmly believed that Germany would inevitably be defeated unless the invasion could be stopped at the beach.
  1944 – World War II: More than 1000 British bombers drop 5,000 tons of bombs on German gun batteries on the Normandy Coast  in preparation for D-Day.