Mock cream made with margarine, ration books, queuing - for the British, food in the Second World War is seen, along with the blackout, as an irritating inconvenience of the Home Front. This was a country bored by the monotony of its diet but never at serious risk of real hunger.

Lizzie Collingham's book provides a salutary shock to such national complacency. In unsensational but detailed prose she widens the lens, showing how acute hunger became "the taste of war" for millions during the Second World War. It was the most deadly weapon, the ultimate sacrifice. In Berlin, in the final, bitter days of fighting in 1945, there was a popular saying: "The fighting won't stop until [the portly] Gör­ing fits into Goebbels's trousers."

Death by starvation is slow and undramatic, and in the annals of war or when war is represented in popular books and films, it is largely ignored. In contrast to slaughter in combat, death from hunger "is very dull", wrote a campaigning journalist during the Bengal famine
of 1943, which killed three million Indians. Yet at least 20 million people died as a result of malnutrition and its associated diseases during the Second World War. Those killed in combat totalled approximately 19.5 million.

To prosecute the war successfully demanded a large and well-equipped army, provisioned with a regular supply of food, medicines and arms. This in turn required a robust industrial base in order to produce the various goods, a prosperous and flexible agricultural sector, able to adapt to wartime conditions and grow the extra food needed to feed the military and those working in heavy war industries, as well as the infrastructure and logistical arrangements necessary to deliver these requirements.

A united home front, a resilient civilian economy, an efficient administration and a government that could raise the finance for war were also essential. During the Second World War very few countries could tick every box on this checklist.

Hunger is the wasting sinew of war, but between 1939 and 1945, it was unlike rationing, intended to ensure that scarce resources were distributed as equitably as possible; its effects were not shared equally. Britain never risked starvation despite the German U-boat blockade that reached its height in November 1942. In the US, far from people starving, agriculture prospered: in effect, America became the larder as well as the arsenal for the Allies during the war. By the time the war was over, the US occupation of the Pacific regions had spread the taste for such delicacies as Coca-Cola and Spam, distorting local economies and creating an insatiable global demand for American food.

Meanwhile, in the Soviet Union, where between two and three million died of starvation, peasant women literally yoked themselves to the plough to till the soil, food was fried in paraffin and at the docks, hordes would grab the garbage thrown from US ships and cram it into their mouths; in Ukraine, students sold litres of their blood for bread and peasants dug up dead horses to consume their flesh; in Greece, 2,000 people a day died of hunger and infant mortality reached 50 per cent; by 1943.

This was also the time when 80 per cent of Belgian children were suffering from rickets, caused by severe vitamin deficiency; minced rectum of cattle and coagulated horse blood spread on bread provided sustenance in the Warsaw Ghetto; in the Bataan Peninsula, the Filipino partisans made stew out of nothing but water and grass.

In Henan, China, where as many as three million died, a woman boiled her baby for food, pleading that it was already dead when it went in the pot, while others skimmed the algae off fetid pools to eat. Potatoes became the universal - often the only - food of war and were often in such short supply that some had only the peelings. Hunger was not merely a by-product of war: it was its engine. Hitler sought to create a thousand-year Reich by making the country self-sufficient and independent of world trade. He regarded the whole of eastern Europe as an industrial site and a food source, and was prepared to let its people starve in his pursuit of Lebensraum for the German-speaking peoples.

Polish Jews, described as being "extremely damaging eaters", were among the first of the millions of Jews despatched to the Nazi death camps. Japan had similar designs on south-east Asia, and was ruthless in leeching food from an already hungry China, Vietnam and Burma to feed its own people. In the wartime hierarchy of hunger, cities took precedence over the countryside and troops came first in the allocation of food; way down at the bottom of the chain were prisoners of war and the victims of racial policies.

In German-occupied parts of the USSR, Jews and children were allowed only 500 calories a day; hundreds of thousands starved, as did 9,000 Soviet prisoners of war each month in the autumn of 1941 alone. "Their care can only be determined by their ability to work for us," Göring decreed.
Although Britain did not suffer acute hunger at home, it exported it: Churchill, who regarded the Quit India Movement as undermining the empire's contribution to Britain's war effort, repeatedly refused requests to increase the shipment of grain to the subcontinent. "How come," he is supposed to have asked, "if India is starving, Gandhi is still alive?"

The Taste of War is an immensely powerful and rightly startling book, presenting a hidden but vital and long-overdue dimension to the history of the Second World War. It is also prescient. As the war ended in May 1945, the UN Food and Agriculture Organisation proposed a World Food Board to stabilise prices and provide a pool of surplus produce from which food aid could be distributed to needy countries. That plan foundered on the national self-interest of Britain and the United States. The war on want remains unwon today.