In the early hours today the Allies began the invasion of Europe by attacking the coast of Normandy with an immense armada of over 4,000 ships and several thousand smaller craft.
Massed airborne landings were successfully effected behind the enemy lines.
British and Canadians have secured beach-heads in at least two points and dug in, states an Associated Press message.
Mr Churchill gave the details of the invasion to the Commons this morning.
He said that the Anglo-American Allies of the Expeditionary Force are sustained by about 11,000 first line aircraft, which can be drawn upon as may be needed for the purposes of battle.
Earlier the Allied 'Communique No 1' had supplied first official news of D-day by stating 'Under the command of General Eisenhower, Allied naval forces, supported by strong air forces, began landing Allied armies this morning on the northern coast of France.
"The landings on the beaches are proceeding at various points at the present time," said the Premier. "The fire of the shore batteries has been largely quelled.
"The obstacles which were constructed in the sea have not proved so difficult as was apprehended.
"So far the commanders who are engaged report that everything is proceeding according to plan - and what a plan.
"This vast operation is undoubtedly the most complicated and difficult which has ever occurred."
Allied forces struck at the whole of north Normandy, according to the German News Agency.
Airbourne landings were made in great depth and the Germans say at least four Anglo-American paratroop and airbourne divisions are taking part.
The Germans say that the whole coastline between Le havre and Cherbourg is involved, with large forces of Allied paratroops trying to seize the airfields in the Normandy peninsula.
This coastline is a stretch of over 100 miles.
Landings took place in the mouth of the Seine and between the Orne and the Vire, the 40 mile piece of coast east of the peninsula.
Heaviest fighting was reported in the area of Caen on the River Orne and nine miles from the coast.
Caen is a strategic centre of communications on the main railway line from Paris to Cherbourg.
A German estimate of the naval forces backing the landings in the Le Havre area is 12 Allied battleships and 40 destroyers.
It is stated in London that the landings took place between 6am and 8.15am following in the wake of the airborne troops.
Minesweepers swept the way into the coast and bomarding ships got into position to engage coastal batteries.
US battleships took part in the bombardment which 'went in the manner planned' according to an official statement.
Allied bombers roaring over at dawn gave British people the first hint that big events were under way.
Almost simultaneously the BBC began warning the French people to get away from coastal areas.
