The Normandy Landings: D-Day: An operation that filled the British with dread: Richard Overy, Professor of Modern History at King's College, London, recounts Churchill's fears

WAS D-Day really necessary? Hardly the question to ask at this moment of dignified, poignant commemoration. Yet in all the hullabaloo we are in danger of forgetting where the invasion fitted into the wider history of the war. D-Day was not always so popular.

Stalin had mixed feelings, having waited so long for his second front. At his meeting with Roosevelt and Churchill at Tehran in November 1943, Stalin finally pressured his allies into committing themselves to invasion. We cannot be certain that the Western powers would have risked it otherwise. Back in Moscow, Stalin told Zhukov, his chief of staff, that it was all the same to him: 'Our own forces are sufficient to complete the rout of Nazi Germany.'

This was not entirely the case, but Soviet forces had borne, and were to continue to bear, the brunt of the Nazi war machine. There were three times as many divisions on the Eastern Front as there were sitting behind the Atlantic Wall. Without effective Soviet resistance in 1943, which tore the heart out of the Nazi military effort, the invasion of France could hardly have been contemplated.

So anxious were they to keep Stalin firmly in the Allied camp that the two Western allies had little choice but to invade. This suited the Americans, who were always much keener to square up to the German army.

The stumbling block all along was Britain. Its leaders always hedged their idea of invasion with conditions and scarcely concealed their anxiety. British resistance prevented any serious effort in 1942. When Churchill persuaded Roosevelt to send American forces to North Africa that autumn, he put paid to any prospect of invasion in 1943. Not until the autumn of 1943 did the British finally, and with great reluctance, accept the American plan to invade in the spring of 1944 and only if, at Churchill's insistence, there were no more than 12 German divisions to oppose them. Stalin later asked: 'What if there are 13?' Churchill had nightmares of the beaches of Normandy 'choked with the flower of American and British youth'. When Stalin, with his characteristic bluntness, asked Churchill to his face if he was willing to invade, he growled back that it was Britain's 'stern duty', but he did not say 'yes'.

Not until three weeks before D-Day, and to the amazement of his American listeners, did Churchill publicly admit that he was coming round to the idea. In his memoirs he gave the whole campaign in France only 30 pages; the Mediterranean got more than 50 for the same period.

Churchill was by no means the only British leader wary of invasion. Brooke, his military chief, wrote in his diary on 5 June that the morrow might bring the most 'ghastly disaster' of the war. The one man on the British side who had unbounded optimism was the ground commander, General Bernard Montgomery, and by a strange irony he is the man that history has unkindly blamed for almost losing the battle.

Why were the British such reluctant conquerors? For Churchill, the ghost of Gallipoli was never far away. That disaster from the First World War had cost him his job and almost cost him his reputation. There were more recent debacles to recall. Britain had been expelled not once, but three times, from the European mainland by German armies: in Norway, at Dunkirk and in Greece.

Another defeat would not only end Churchill's career, but would spell the collapse of British military and political credibility. For America there were no defeats to redeem: for Britain, another defeat in France would have been a catastrophe.

British leaders saw only one way out of their dilemma - they wanted to wage war the British way, through blockade and attrition, fighting small wars at the periphery. Britain simply lacked the resources for anything bigger. This was the strategy settled on in the middle of the war: bombing to wear down the enemy, a Mediterranean theatre to eat away at Axis strengths.

The American way held all kinds of other risks. The British were well aware that the balance in the grand alliance was tilting towards the USSR and the US. A frontal assault on Nazi Europe, whatever its military drawbacks, was impossible without American aid and would inevitably mean much larger American forces.

The US could afford the losses and costs, whereas Britain was stretched to the limit by 1944. The final decision to invade marked the point in the war when the two incipient super-powers began at last to flex their political muscles.

The growing tension between the two Western powers - the ageing empire and the young, ebullient successor - never produced an open rift, though it led to endless squabbles and recrimination before the invasion and long after its extraordinary success.

The commander was an American, General Dwight D Eisenhower, who, many British generals scornfully observed, had never seen combat. Consciously or not, the British got their own back by appointing Montgomery as the ground commander for the invasion. For all his strengths, Monty was an almost impossible man to work with. He tried Eisenhower's legendary forbearance to its limits. The tension between the two powers was personified in the two generals' uneasy relationship.

There was worse to come. Eisenhower wanted bomber support, but the bomber barons wanted to win the war their way, by destroying German industry and the Luftwaffe, and would not throw their weight behind invasion. Eisenhower was brought to the brink of nervous collapse. By March 1944 he was close to resigning, saying: 'Tell the Prime Minister to get someone else to run this damn war. I'll quit'.

Even when he got his way with the bombers there was still Churchill, smarting at the collapse of his Mediterranean gambit. He refused to sanction bombing of French communications for fear of French losses, until yet another resignation threat forced his hand.

The arguments persisted. Safely ashore in France, Montgomery conserved his strength and played a strategy of patient attrition. American opinion wanted quick results and American heroes. Montgomery approached war like a cricket match of four innings' duration; Eisenhower saw it like an American football game. After seven weeks of apparent stalemate, Montgomery was closer than he realised to the sack. American impatience could barely be contained. When the break-out finally came, no one thanked Montgomery. American armies hurtled their way across France, hustling aside their weaker partner. The rest of the campaign was dictated by Eisenhower. When he assumed effective command in Europe the unequal balance between the Allies was clear. Britain had no more reserves on which to draw. American power, economic at first, but now military, must at the time have appeared limitless.

In the end, for all the arguments and half-heartedness, D-Day mattered more than Stalin thought. Against British fears, it proved possible to defeat Germany's western armies through a combination of massive air power, shrewd deception, and a plan of campaign that succeeded despite American frustration at the lack of exuberant aggression. After the victory in France, there was no question that Hitler would be defeated; Allied defeat on the beaches might have allowed 50 German divisions to swing eastwards, and the employment of a whole range of new weapons - jets, rockets, new submarines. But these would merely have postponed German defeat.

The invasion of France meant the populations of western Europe were, to their relief, liberated by the democracies and not by the Red Army. And it allowed the Western allies to share in the reconstruction of post-war Europe, and American preponderance ensured that this time the US would feel more fully a part of that process than in 1919. If the British had had their way in 1943, the final outcome would surely have been very different. The US was never far from shifting priority to the Pacific if the British proved obdurate. Hemmed in by the Alps and the Balkan ranges, the Western allies would have been spectators at the defeat and occupation of Germany. D-Day made strategic sense.

There was little point regretting the transfer of international power made possible by victory in France. If that transfer had been made sooner, Europe might have been spared war altogether.

(Photograph omitted)