Operation Neptune was the maritime counterpart of Operation Overlord, the allied landing in Normandy that started at 6 June 1944, the day that is better known as D-Day. All maritime operations in Normandy from 6 June until 90 days later were designated with the name Operation Neptune. These operations included the transport of troops and vehicles, the escorting of landing craft, the distraction of the German navy and air force and the further supply over seas. The construction of two temporary artificial harbours with code name Mulberry and the five breakwaters designated by the name Gooseberry also ressorted under Operation Neptune.
For Operation Neptune, the largest fleet of all times was gathered on the south coast of England. The armada consisted of, among other, no less than 1,213 warships varying from battleships to midget submarines. Over three quarters of these were either British or British/Canadian. 16,5 per cent was of American origin and 4,5 per cent was supplied by the navies from other allied countries like France, Poland, Norway, Greece and The Netherlands. The rest of the fleet that was destined to carry out Operation Neptune consisted of 4,126 merchant ships. This was a motley collection of adapted and specially designed ships, landing craft and troop transporters. There were many large and small passenger ships that had been converted to Landing Ship Tank (LST), Landing Ship Infantry (LSI), or Landing Ship Material (LSM). Many of these ships had landing craft on board that were designated as Landing Craft Assault (LCA), Landing Craft Tank (LCT) and Landing Craft Support (LCS). Besides, there were adapted ships for laying smoke screens or buoys, rescue vessels, hospital ships, tugs and even floating docks. Over three quarters of these ships sailed under the British flag, but the largest part was built in the United States and was transferred to the British on the basis of the Lend Lease Act.
This enormous fleet of 5,339 schips was on Sunday 4 June 1944 in position in the Channel when word was received that the invasion had been postponed from 5 June to 6 June. A part of the fleet cruised back and forth along the English south coast. Because of the bad weather circumstances the Germans held their reconnaissance planes grounded so that this unusual large concentration of ships remained unseen. This was essential for the whole plan of attack of the allies. The chance of success depended for a large part on the element of surprise. In the evening of 5 June 1944 the order "carry out Operation Neptune" was given by the British Admiral Bertram Ramsay, commander in chief of Neptune. The assembled fleet set itself in motion, from the Isle of Wight, in ten columns through ten small routes that had been cleared of mines. The routes were marked by buoys that had been laid at distances of five miles.
The Dutch contribution to Operation Neptune consisted of four warships, two tankers, twelve freighters and transporters, twelve tugs, eight fishing trawlers and tens of coastal vessels. On 1 July 1940 in Londen, the Netherlands Shipping & Trading Committee (NSTC) was established. This commission superintended the so called Vaarplichtwet, a law that obliged Dutch sailors to continue sailing on board of their own ship or on another allied ship. The NSTC was soon known by every Dutch sailor as the Shipping. Dutch vessels that managed to evacuate to England were registered with the NSTC. In this way they could be deployed in war tasks like Operation Dynamo, the evacuating of British and French troops from Dunkirk. Most of the Dutch ships that took part in Operation Neptune were deployed by the British Ministry of War Transport by entering into a special Liberator Charter. With this charter, the Dutch government took over all obligations to the crews of the ships in question. Like all charter contracts, the Liberator Charter was a so called timecharter, a renting period for a certain time.