R.M. Douglas is the author of “Orderly and Humane: The Expulsion of the Germans after the Second World War” (Yale University Press, $38)

In December 1944 Winston Churchill announced to a startled House of Commons that the Allies had decided to carry out the largest forced population transfer — or what is nowadays referred to as “ethnic cleansing” — in human history.

Millions of civilians living in the eastern German provinces that were to be turned over to Poland after the war were to be driven out and deposited among the ruins of the former Reich, to fend for themselves as best they could. The Prime Minister did not mince words. What was planned, he forthrightly declared, was “the total expulsion of the Germans… For expulsion is the method which, so far as we have been able to see, will be the most satisfactory and lasting.”

The Prime Minister’s revelation alarmed some commentators, who recalled that only eighteen months previously his government had pledged: “Let it be quite clearly understood and proclaimed all over the world that we British will never seek to take vengeance by wholesale mass reprisals against the general body of the German people.”

In the United States, senators demanded to know when the Atlantic Charter, a statement of Anglo-American war aims that affirmed the two countries’ opposition to “territorial changes that do not accord with the freely expressed wishes of the people concerned” had been repealed. George Orwell, denouncing Churchill’s proposal as an “enormous crime,” took comfort in the reflection that so extreme a policy “cannot actually be carried through, though it might be started, with confusion, suffering and the sowing of irreconcilable hatreds as the result.”

Orwell greatly underestimated both the determination and the ambition of the Allied leaders’ plans. What neither he nor anybody else knew was that in addition to the displacement of the 7-8 million Germans of the East, Churchill, U.S. President Franklin D. Roosevelt and Soviet leader Joseph Stalin had already agreed to a similar “orderly and humane” deportation of the more than 3 million German-speakers — the “Sudeten Germans” — from their homelands in Czechoslovakia. They would soon add the half-million ethnic Germans of Hungary to the list.

Although the governments of Yugoslavia and Romania were never given permission by the Big Three to deport their German minorities, both would take advantage of the situation to drive them out also.

By mid-1945, not merely the largest forced migration but probably the largest single movement of population in human history was under way, an operation that continued for the next five years. Between 12 and 14 million civilians, the overwhelming majority of them women, children and the elderly, were driven out of their homes or, if they had already fled the advancing Red Army in the last days of the war, forcibly prevented from returning to them.

From the beginning, this mass displacement was accomplished largely by state-sponsored violence and terror. In Poland and Czechoslovakia, hundreds of thousands of detainees were herded into camps — often, like Auschwitz I or Theresienstadt, former Nazi concentration camps kept in operation for years after the war and put to a new purpose.

The regime for prisoners in many of these facilities was brutal, as Red Cross officials recorded, with beatings, rapes of female inmates, gruelling forced labour and starvation diets of 500-800 calories the order of the day. In violation of rarely-applied rules exempting the young from detention, children routinely were incarcerated, either alongside their parents or in designated children’s camps. As the British Embassy in Belgrade reported in 1946, conditions for Germans “seem well down to Dachau standards.”

Though the death rates in the camps were often frighteningly high — 2,227 inmates of the Mysłowice facility in southern Poland alone perished in the last ten months of 1945 — most of the mortality associated with the expulsions occurred outside them.

Forced marches in which inhabitants of entire villages were cleared at fifteen minutes’ notice and driven at rifle-point to the nearest border, accounted for many losses. So did train transports that sometimes took weeks to reach their destination, with up to 80 expellees crammed into each cattle car without adequate (or, occasionally, any) food, water or heating.

The deaths continued on arrival in Germany itself. Declared ineligible by the Allied authorities to receive any form of international relief and lacking accommodation in a country devastated by bombing, expellees in many cases spent their first months or years living rough in fields, goods wagons or railway platforms.

Malnutrition, hypothermia and disease took their toll, especially among the very old and very young. Although more research is needed to establish the total number of deaths, conservative estimates suggest that some 500,000 people lost their lives as a result of the operation.

Not only was the treatment of the expellees in defiance of the principles for which the Second World War had professedly been fought, it created numerous and persistent legal complications. At the Nuremberg trials, for example, the Allies were trying the surviving Nazi leaders on charges of carrying out “deportation and other inhumane acts” against civilian populations at the same moment as, less than a hundred miles away, they were engaging in large-scale forced removals of their own.

Similar problems arose with the UN’s 1948 Genocide Convention, the first draft of which outlawed the “forced and systematic exile of individuals representing the culture of a group.” This provision was deleted from the final version at the insistence of the U.S. delegate, who pointed out that it “might be interpreted as embracing forced transfers of minority groups such as have already been carried out by members of the United Nations.”

To the present day, expelling states continue to go to great lengths to exclude the deportations and their continuing effects from the reach of international law. In October 2009, for example, the current President of the Czech Republic, Václav Klaus, refused to sign the European Union’s Lisbon Treaty unless his country was granted an “exemption” ensuring that surviving expellees could not use the Treaty to seek redress for their maltreatment in the European courts. Facing the collapse of the accord in the event of Czech non-ratification, the EU reluctantly acquiesced.

To this day, the postwar expulsions — the scale and lethality of which vastly exceed the ethnic cleansing that accompanied the break-up in the 1990s of the former Yugoslavia — remain little known outside Germany itself. (Even there, a 2002 survey found that Germans under thirty had a more accurate knowledge of Ethiopia than of the areas of Europe from which their grandparents were deported.)

The textbooks on modern German and modern European history I use regularly in my college classroom either omit mention of the expulsions altogether, or relegate them to a couple of uninformative, and frequently inaccurate, lines depicting them as the inevitable consequence of Germany’s wartime atrocities. In popular discourse, on the rare occasions that the expulsions are mentioned at all it is common to dismiss them with the observation that the expellees were “got what they deserved,” or that the interest of the expelling states in unburdening themselves of a potentially disloyal minority population should take precedence over the deportees’ right to remain in the lands of their birth.

Superficially persuasive as these arguments may appear, they do not stand up to scrutiny. The expellees were deported not after individual trial and conviction for acts of wartime collaboration — something of which the children could not have been guilty in any event — but because their indiscriminate removal served the interests of the Great Powers and the expelling states alike.

Provisions to exempt proven “anti-fascists” from detention or transfer were routinely ignored by the very governments that adopted them; Oskar Schindler, the most famous “anti-fascist” of all who had been born in the Czech town of Svitavy, was deprived by the Prague authorities of nationality and property like the rest.

The proposition, moreover, that it is legitimate in some circumstances to declare in respect of entire populations that considerations of human rights are simply not to apply is an exceedingly dangerous one. Once the principle that certain specially disfavoured groups may be treated in this way is admitted, it is hard to see why it should not be applied to others. Scholars including Andrew Bell-Fialkoff, John Mearsheimer and Michael Mann have already pointed to the expulsion of the Germans as an encouraging precedent for the organization of similar forced migrations in the former Yugoslavia, the Middle East and elsewhere.

The history of the postwar expulsions, though, shows that there is no such thing as an “orderly and humane” transfer of populations: violence, cruelty and injustice are intrinsic to the process. As the former U.S. Secretary of State Madeleine Albright, who fled Nazi-occupied Czechoslovakia as a small child, has correctly noted: “Collective punishments, such as forced expulsions, are usually rationalized on the grounds of security but almost always fall most heavily on the defenseless and weak.”

It is important to bear in mind that no valid comparison may be drawn between the expulsion of the Germans and the far greater atrocities for which Nazi Germany was responsible. Suggestions to the contrary — including those made by expellees themselves — are both offensive and historically illiterate.

Nonetheless, as the historian B.B. Sullivan has observed in another context, “greater evil does not absolve lesser evil.” The postwar expulsions were by any measure one of the most significant occurrences of the mass violation of human rights in recent history. Their demographic, economic, cultural and political effects continue to cast a long and baleful shadow across the European continent. Yet their importance remains unacknowledged, and many vital aspects of their history have not been adequately studied.

Nearly seventy years after the end of the Second World War, as the last surviving expellees are passing from the scene, the time has come for this tragic and destructive episode to receive the attention it deserves, so that the lessons it teaches may not be lost and the unnecessary suffering it engendered may not be repeated.