As we recall the Red Army’s liberation of Auschwitz on January 27, 1945, sixty-six years ago today, we might ask: who was worse, Hitler or Stalin?

In the second half of the twentieth century, Americans were taught to see both Nazi Germany and the Soviet Union as the greatest of evils. Hitler was worse, because his regime propagated the unprecedented horror of the Holocaust, the attempt to eradicate an entire people on racial grounds. Yet Stalin was also worse, because his regime killed far, far more people—tens of millions, it was often claimed—in the endless wastes of the Gulag. For decades, and even today, this confidence about the difference between the two regimes—quality versus quantity—has set the ground rules for the politics of memory. Even historians of the Holocaust generally take for granted that Stalin killed more people than Hitler, thus placing themselves under greater pressure to stress the special character of the Holocaust, since this is what made the Nazi regime worse than the Stalinist one.

Discussion of numbers can blunt our sense of the horrific personal character of each killing and the irreducible tragedy of each death. As anyone who has lost a loved one knows, the difference between zero and one is an infinity. Though we have a harder time grasping this, the same is true for the difference between, say, 780,862 and 780,863—which happens to be the best estimate of the number of people murdered at Treblinka. Large numbers matter because they are an accumulation of small numbers: that is, precious individual lives. Today, after two decades of access to Eastern European archives, and thanks to the work of German, Russian, Israeli, and other scholars, we can resolve the question of numbers. The total number of noncombatants killed by the Germans—about 11 million—is roughly what we had thought. The total number of civilians killed by the Soviets, however, is considerably less than we had believed. We know now that the Germans killed more people than the Soviets did. That said, the issue of quality is more complex than was once thought. Mass murder in the Soviet Union sometimes involved motivations, especially national and ethnic ones, that can be disconcertingly close to Nazi motivations.

It turns out that, with the exception of the war years, a very large majority of people who entered the Gulag left alive. Judging from the Soviet records we now have, the number of people who died in the Gulag between 1933 and 1945, while both Stalin and Hitler were in power, was on the order of a million, perhaps a bit more. The total figure for the entire Stalinist period is likely between two million and three million. The Great Terror and other shooting actions killed no more than a million people, probably a bit less. The largest human catastrophe of Stalinism was the famine of 1930–1933, in which more than five million people starved.

Of those who starved, the 3.3 million or so inhabitants of Soviet Ukraine who died in 1932 and 1933 were victims of a deliberate killing policy related to nationality. In early 1930, Stalin had announced his intention to “liquidate” prosperous peasants (“kulaks”) as a class so that the state could control agriculture and use capital extracted from the countryside to build industry. Tens of thousands of people were shot by Soviet state police and hundreds of thousands deported. Those who remained lost their land and often went hungry as the state requisitioned food for export. The first victims of starvation were the nomads of Soviet Kazakhstan, where about 1.3 million people died. The famine spread to Soviet Russia and peaked in Soviet Ukraine. Stalin requisitioned grain in Soviet Ukraine knowing that such a policy would kill millions. Blaming Ukrainians for the failure of his own policy, he ordered a series of measures—such as sealing the borders of that Soviet republic—that ensured mass death.

In 1937, as his vision of modernization faltered, Stalin ordered the Great Terror. Because we now have the killing orders and the death quotas, inaccessible so long as the Soviet Union existed, we now know that the number of victims was not in the millions. We also know that, as in the early 1930s, the main victims were the peasants, many of them survivors of hunger and of concentration camps. The highest Soviet authorities ordered 386,798 people shot in the “Kulak Operation” of 1937–1938. The other major “enemies” during these years were people belonging to national minorities who could be associated with states bordering the Soviet Union: some 247,157 Soviet citizens were killed by the NKVD in ethnic shooting actions.

In the largest of these, the “Polish Operation” that began in August 1937, 111,091 people accused of espionage for Poland were shot. In all, 682,691 people were killed during the Great Terror, to which might be added a few hundred thousand more Soviet citizens shot in smaller actions. The total figure of civilians deliberately killed under Stalinism, around six million, is of course horribly high. But it is far lower than the estimates of twenty million or more made before we had access to Soviet sources. At the same time, we see that the motives of these killing actions were sometimes far more often national, or even ethnic, than we had assumed. Indeed it was Stalin, not Hitler, who initiated the first ethnic killing campaigns in interwar Europe.

Until World War II, Stalin’s regime was by far the more murderous of the two. Nazi Germany began to kill on the Soviet scale only after the Molotov-Ribbentrop Pact in the summer of 1939 and the joint German-Soviet invasion of Poland that September. About 200,000 Polish civilians were killed between 1939 and 1941, with each regime responsible for about half of those deaths. This figure includes about 50,000 Polish citizens shot by German security police and soldiers in the fall of 1939, the 21,892 Polish citizens shot by the Soviet NKVD in the Katyn massacres of spring 1940, and the 9,817 Polish citizens shot in June 1941 in a hasty NKVD operation after Hitler betrayed Stalin and Germany attacked the USSR. Under cover of the war and the occupation of Poland, the Nazi regime also killed the handicapped and others deemed unfit in a large-scale “euthanasia” program that accounts for 200,000 deaths. It was this policy that brought asphyxiation by carbon monoxide to the fore as a killing technique.

Beyond the numbers killed remains the question of intent. Most of the Soviet killing took place in times of peace, and was related more or less distantly to an ideologically-informed vision of modernization. Germany bears the chief responsibility for the war, and killed civilians almost exclusively in connection with the practice of racial imperialism. Germany invaded the Soviet Union with elaborate colonization plans. Thirty million Soviet citizens were to starve, and tens of millions more were to be shot, deported, enslaved, or assimilated. Such plans, though unfulfilled, provided the rationale for the bloodiest occupation in the history of the world. The Germans placed Soviet prisoners of war in starvation camps, where 2.6 million perished from hunger and another half million (disproportionately Soviet Jews) were shot. A million Soviet citizens also starved during the siege of Leningrad. In “reprisals” for partisan action, the Germans killed about 700,000 civilians in grotesque mass executions, most of them Belarusians and Poles. At the war’s end the Soviets killed tens of thousands of people in their own “reprisals,” especially in the Baltic states, Belarus, and Ukraine. Some 363,000 German soldiers died in Soviet captivity.

Hitler came to power with the intention of eliminating the Jews from Europe; the war in the east showed that this could be achieved by mass killing. Within weeks of the attack by Germany (and its Finnish, Romanian, Hungarian, Italian, and other allies) on the USSR, Germans, with local help, were exterminating entire Jewish communities. By December 1941, when it appears that Hitler communicated his wish that all Jews be murdered, perhaps a million Jews were already dead in the occupied Soviet Union. Most had been shot over pits, but thousands were asphyxiated in gas vans. From 1942, carbon monoxide was used at the death factories Chełmno, Bełżec, Sobibór, and Treblinka to kill Polish and some other European Jews. As the Holocaust spread to the rest of occupied Europe, other Jews were gassed by hydrogen cyanide at Auschwitz-Birkenau.

Overall, the Germans, with much local assistance, deliberately murdered about 5.4 million Jews, roughly 2.6 million by shooting and 2.8 million by gassing (about a million at Auschwitz, 780,863 at Treblinka, 434,508 at Bełzec, about 180,000 at Sobibór, 150,000 at Chełmno, 59,000 at Majdanek, and many of the rest in gas vans in occupied Serbia and the occupied Soviet Union). A few hundred thousand more Jews died during deportations to ghettos or of hunger or disease in ghettos. Another 300,000 Jews were murdered by Germany’s ally Romania. Most Holocaust victims had been Polish or Soviet citizens before the war (3.2 million and 1 million respectively). The Germans also killed more than a hundred thousand Roma.

All in all, the Germans deliberately killed about 11 million noncombatants, a figure that rises to more than 12 million if foreseeable deaths from deportation, hunger, and sentences in concentration camps are included. For the Soviets during the Stalin period, the analogous figures are approximately six million and nine million. These figures are of course subject to revision, but it is very unlikely that the consensus will change again as radically as it has since the opening of Eastern European archives in the 1990s. Since the Germans killed chiefly in lands that later fell behind the Iron Curtain, access to Eastern European sources has been almost as important to our new understanding of Nazi Germany as it has been to research on the Soviet Union itself. (The Nazi regime killed approximately 165,000 German Jews.)

Apart from the inacessibilty of archives, why were our earlier assumptions so wrong? One explanation is the cold war. Our wartime and postwar European alliances, after all, required a certain amount of moral and thus historical flexibility. In 1939 Germany and the Soviet Union were military allies. By the end of 1941, after the Germans had attacked the Soviet Union and Japan the United States, Moscow in effect had traded Berlin for Washington. By 1949, the alliances had switched again, with the United States and the Federal Republic of Germany together in NATO, facing off against the Soviet Union and its Eastern European allies, including the smaller German Democratic Republic. During the cold war, it was sometimes hard for Americans to see clearly the particular evils of Nazis and Soviets. Hitler had brought about a Holocaust: but Germans were now our allies. Stalin too had killed millions of people: but the some of the worst episodes, taking place as they had before the war, had already been downplayed in wartime US propaganda, when we were on the same side.

We formed an alliance with Stalin right at the end of the most murderous years of Stalinism, and then allied with a West German state a few years after the Holocaust. It was perhaps not surprising that in this intellectual environment a certain compromise position about the evils of Hitler and Stalin—that both, in effect, were worse—emerged and became the conventional wisdom.

New understandings of numbers, of course, are only a part of any comparison, and in themselves pose new questions of both quantity and quality. How to count the battlefield casualties of World War II in Europe, not considered here? It was a war that Hitler wanted, and so German responsibility must predominate; but in the event it began with a German-Soviet alliance and a cooperative invasion of Poland in 1939. Somewhere near the Stalinist ledger must belong the thirty million or more Chinese starved during the Great Leap Forward, as Mao followed Stalin’s model of collectivization. The special quality of Nazi racism is not diluted by the historical observation that Stalin’s motivations were sometimes national or ethnic. The pool of evil simply grows deeper.

The most fundamental proximity of the two regimes, in my view, is not ideological but geographical. Given that the Nazis and the Stalinists tended to kill in the same places, in the lands between Berlin and Moscow, and given that they were, at different times, rivals, allies, and enemies, we must take seriously the possibility that some of the death and destruction wrought in the lands between was their mutual responsibility. What can we make of the fact, for example, that the lands that suffered most during the war were those occupied not once or twice but three times: by the Soviets in 1939, the Germans in 1941, and the Soviets again in 1944?

The Holocaust began when the Germans provoked pogroms in June and July 1941, in which some 24,000 Jews were killed, on territories in Poland annexed by the Soviets less than two years before. The Nazis planned to eliminate the Jews in any case, but the prior killings by the NKVD certainly made it easier for local gentiles to justify their own participation in such campaigns. As I have written in Bloodlands, where all of the major Nazi and Soviet atrocities are discussed, we see, even during the German-Soviet war, episodes of belligerent complicity in which one side killed more because provoked or in some sense aided by the other. Germans took so many Soviet prisoners of war in part because Stalin ordered his generals not to retreat. The Germans shot so many civilians in part because Soviet partisans deliberately provoked reprisals. The Germans shot more than a hundred thousand civilians in Warsaw in 1944 after the Soviets urged the locals to rise up and then declined to help them. In Stalin’s Gulag some 516,543 people died between 1941 and 1943, sentenced by the Soviets to labor, but deprived of food by the German invasion.

Were these people victims of Stalin or of Hitler? Or both?