“YOU are about to embark up on the Great Crusade, toward which we have striven these many months.”

So began a letter from General Dwight D Eisenhower, supreme commander of the Allied Expeditionary Forces, to the 156,000 who were about to take part in the attempt to storm the beaches of northern France.

“The eyes of the world are upon you. The hopes and prayers of liberty-loving people everywhere march with you,” he went on.

But as the troops sailed on D-Day – June 6, 1944 – Eisenhower also wrote a statement to be released if the operation failed. Either enemy action or the weather in the Channel could easily scupper the operation to finally liberate Europe from Germany.

D-Day 75, a new commemorative publication by the Daily Echo and other local newspapers in the Newsquest group, tells the local story of D-Day.

Dorset played a crucial role in the preparations for the Normandy landings.

Amphibious Valentine tanks were tested in mock assaults on Studland Beach.

And in March 1944, a 12-mile fuel pipe was laid underwater from Poole to the Isle of Wight. Known as PLUTO (pipeline under the ocean), it was built to test the feasibility of laying a pipe from the Isle of Wight to the beaches of Normandy.

The experiment was a success and, a month later, King George VI was among the VIPs who visited Fort Henry and Studland to watch a mock invasion by the 1st Battalion of the Dorset Regiment.

As D-Day approached, the war effort in Poole went into overdrive.

J Bolson & Sons, with a staff of 800, became the biggest producer of landing craft in the UK, its efforts supplemented by those of the Dorset Yacht Company.

The British Power Boat Company, on West quay Road, produced motor gun boats, while RA Newman’s of Hamworthy was building launches.

Newman’s and Sydenhams made wooden decking for the Mulberry harbours that would be taken to Normandy, while engineering firm JR S mith produced parts for Bailey Bridges.

Most of the troops would be embarking from Poole were American. They were billeted off Herbert Avenue, while Carters Pottery on the Quay was a headquarters fo the US Army.

Meanwhile, an amphibious training centre, HMS Turtle, set up in Hamworthy.

On June 5, the first 300 vessels set sail from Poole, bound for the beaches of Normandy. The harbour went from packed to empty as the first of 22,000 troops left for Omaha beach.

D-Day 75 tells the story of preparations across the south coast, but it also tells the smaller and more personal stories.

There is the tale of Poole’s Sgt Norman Knight, who was unit photographer in the Pay Corps at Leicester. He was hired to take photographs of Lt Clifton ‘Jimmy’ James, who bore an astonishing resemblance to Field Marshall Bernard Montgomery. The idea of photographing Monty’s lookalike in Gibraltar and North Africa was to help deceive the Nazis into thinking no invasion of France was imminent – and the whole episode was dramatised in the film I Was Monty’s Double.

The real Field Marshall Montgomery was once spotted at Bournemouth’s Carlton Hotel, where he and General Eisenhower surveyed the troops and boats massed in Poole Bay before taking lunch and discussing the rehearsals for the invasion. A local schoolboy, Jim Wilson, was watching them and later became managing director of the hotel.

Many of the 156,000 who took part in the June 6 landings faced heavy resistance, and 10,000 of them would become casualties, with 2,500 killed.

But the operation was a success. By the end of that first day, the Allies had a foothold in Northern France.

Over the next two months, more than 1.5million men and 1.6m tons of supplies were landed. The operation would cost almost 37,000 Allied lives and leave 65,000 Germans dead – but in the following months, occupied Europe would be liberated.

D-Day 75 costs £1.50 and is available wherever you buy your Daily Echo, with 15p from every copy going to a military charity.