First came GEE, which covered north-west Europe with an invisible lattice of intersecting signals sent from three stations in south-east England...then, in December 1942, the most precise aid of all, Oboe. Again relying on signals from Britain, out to a radius of some 400 km (250 miles), this could guide aircraft with an accuracy of some 100 meters.

In January 1943 bombers began using H2S. It was heavy, disrupted bomber production, made it impossible to fit the turret or even a window to defend against a night fighter underneath, and behaved like a lighthouse broadcasting the bomber's position to those same night fighters. It was also extremely difficult to use, but it had the advantage that it could not be jammed by the enemy, went wherever the bomber went and, in the hands of a skilled operator, enabled bombs or target indicators to be dropped accurately even over unbroken mist or cloud.

The Pathinder Force (PFF) began operating from August 1942. Their marking, by Lancasters using H2S and Mosquitoes with Oboe, absolutely transformed Bomber Command's operations. As the striking power of the force grew, so did Harris' leadership not only keep morale sky-high but he insisted on trying to get more aircraft over the target in the shortest time, and thus saturate the defences and allow more aircraft to return unscathed.

Bomber Command's attacks, initially a mere nuisance, became what Hitler's armaments minister, Albert Speer, called "the greatest battle that we lost." On May 15, 1940, 93 bombers set out for the Krupp works at Essen. In a later assessment it was calculated that the proportion of bombs that actually it the vast factories was 3 percent. In contrast, in a massive attack by 705 "heavies" on July 25, 1943, marked by Oboe-equipped Pathfinders, the proportion was assessed at 96 percent.

The camaraderie of the crew was crucial. Morale was sustained by the knowledge that one was part of the best crew in Bomber Command which almost everyone believed he was. Who were these aircrew? In many squadrons anyone as old as 25 might be called grandpa, and have to serve as a father-confessor, or as CO pass on sad news to next of kin. Family background counted for nothing. Ability, and the ability to inspire confidence in others, counted for everything.... Rare indeed was the crew who doubted the worth of one of their number. And not least of the remarkable factors is that the surviving crews, who became closely knit into a single instantly reacting unit, were made up of a mix of nationalities, ranks and family backgrounds.

In the 1930's nobody could have foreseen that soon Britain would be isolated off the shore of a German-held continent, nor that it would be possible for Bomber Command to lose more than 500 aircrew in a single night. The beleaguered wartime island could never have trained aircrew in anything remotely like the numbers needed, yet it is surely remarkable that this gigantic (Commonwealth Air Training) plan should by late 1944 have trained 131,553 aircrew in Canada, 23,262 in Australia, Zealand and over 13,000 (all pilots) in the USA. Most of this enormous output then came to Britain to be honed to operational standard.

By 1941 cities throughout Europe had been bombed by the Luftwaffe, and helpless refugees had been machine-gunned from the air. These missions were flown with the sole objective of terrorising the civilian population, and breaking any will to resist. In 1940-42 the Luftwaffe devastated London, Coventry, Southampton, Bristol, Plymouth, Sheffield, Liverpool, Cardiff, Glasgow and many other British cities. From April 1942 its raids on Britain were specifically redirected against cities distinguished by three stars in the Baedeker guidebook as being "of outstanding historic or artistic interest."

By 1941 the United Kingdom was isolated as the only part of Europe still holding out against Hitler. Ringed by U-boats and suffering heavy air attack, it had no means of hitting back except by Bomber Command.

Bomber Command's targets were selected by the War Cabinet, who were themselves influenced by the suggestions of the Ministry of Economic Warfare. The Commander-in-Chief, who from February 22, 1942 was Sir Arthur Harris, could not dictate policy (though he could offer advice). His duty was to assign targets and units to carry out the orders given to him.

Nobody can reduce to tidy arithmetic the overall effect of the devastation of Germany, nor what might have been done had the same effort been applied to some other method of waging war (but what?). Common sense surely tells us that, without the sustained attacks on Hitler's war machine, D-Day could have been a costly failure. In any case, without Bomber Command, and the equally courageous daytime attacks by the US Army 8th Air Force, it is difficult to imagine what could have been a viable alternative.

Today few people have any idea of the tremendous role played by Bomber Command in winning the war. How many know that, because it destroyed the majority of the huge barges Hitler expected would bring his armies to invade Britain losing 718 aircrew in the process, compared with 497 by Fighter Command even if the Battle of Britain had been lost, a successful invasion would almost certainly have been impossible? Without any public adulation, Bomber Command then sank seven of Hitler's 15 major warships, annihilated his merchant fleet and destroyed or "contracepted" hundreds of his U-boats.

Hitler's production czar, Albert Speer, said:The bombing of Germany deprived the German forces of 75 percent of their heavy anti-tank-guns, scattered all over Germany because we never knew where the bombers would strike next. Field Marshal Milch had 900,000 fit soldiers manning those guns. In addition, hundreds of thousands of expert tradesmen could not be called up into the Army because their skills were needed to repair bomb damage. "Dr. Horst Borg, Chief Historian in the Military History Office in Freiburg, notes that, "the aluminum in the fuses of the flak shells would have built 40,000 additional fighter aircraft."

Nobody can say how many British lives were saved by the attack on the rocket laboratory at Peenemunde, and on the flying-bomb transport network and launch sites, but it must be many thousands. When the Allied armies were well established in France after D-Day Field Marshal Rommel said, "Stop the bombers or we can't win!" Nobody can say how many British soldiers were saved by bombing Le Havre; the city was taken, giving the Allies their first Channel port at the cost of 30 British troops, whilst rounding up 11,000 demoralised Germans. Bombers stopped Sepp Dietrich's armour in the Ardennes (the Battle of the Bulge) by cutting all his supply routes; Gen. Dietrich later said, "Not even the best troops in the world can stand up to this heavy bombing."

Repeatedly, whenever the Allied armies were held up by stubborn resistance, Bomber Command was always on call to eliminate the opposition. Their culminating achievement in such operations was to allow the British Army to cross the Rhine at Wesel with just 36 casualties, instead of the thousands which had been expected.