As the much-vaunted "model" concentration camp, the place where future SS camp commandants learned their trade, Dachau was not only the first camp which Heinrich Himmler founded in 1933. It was also, as it turned out, one of the last to be liberated in 1945. This meant that, by the time US troops reached Dachau on April 29, the camp was full of the dying and the dead.

As the SS dragged concentration camp prisoners, around the dwindling territory of the Third Reich in a vain attempt to prevent their falling into Allied hands, Dachau became an end station for these lethal death marches. The 45th "Thunderbird" Division found the camp, crammed with 35,000 survivors, they also found thousands of corpses, which, for want of fuel to burn them, had been stacked like firewood outside the infirmary and crematorium. Even before they reached the camp, they came upon the aftermath of one of the last evacuations from the camp at Buchenwald; an abandoned train of forty cattle trucks loaded with 2,000 prisoners. Those who had staggered out of the trucks had been shot down by the SS. By the time the Americans arrived, only seventeen people showed any signs of life; all were beyond help.

Nothing had prepared the US soldiers for these sights. In the next few days, they were also astonished to see local residents pushing their bicycles down the camp road, passing the goods train and its freight of the dead with apparent unconcern, literally unflinching in attaining their goal of looting the former SS stores (Dachau had also housed the major SS training camp and central supply depot). What different groups of people looked at and what they chose to dwell on were already poles apart.

After an immediate deluge of international political and media attention, which imprinted the name of Dachau on to the memory of a mass audience as a key symbol of Nazi atrocities, the US occupation authorities turned the site into an internment camp for suspected Nazi war criminals. With the onset of the Cold War in 1947, Washington pushed for a speedy and unheroic end to such persecutions, and the camp was handed back to the Bavarian authorities, who used the barracks to accommodate ethnic German refugees and expellees from Eastern Europe until the early 1960s.

When we look back at this period, in which the exigencies of the Cold War led the Western allies to connive at a wholesale restitution of the administrative, military, police and judicial personnel of the Nazi State – to a point where some ministries had a higher saturation of former Nazi Party members in the 1950s than they had had during the Third Reich – it remains something of a minor miracle that former concentration camps like Dachau were not simply dismantled. Key figures in the local Dachau and Bavarian State governments certainly attempted to do so.

One of the main reasons the authorities failed to tear down Dachau was the well-organized opposition of survivor groups. The Bavarian authorities got as far as dismantling the watchtowers before Fr Leonard Roth intervened. This remarkable man, imprisoned and particularly badly treated in Dachau by the SS (he was categorized as an "Asocial", rather than as a political prisoner), stayed an after the war as priest, first to the SS men interned there and then to the ethnic Germans who were housed in the camp during the 1950s. He, and others like him, built tenuous links between these new camp residents and the former concentration camp prisoners. This task was carried out often despite opposition from the local Dachau notables, the Catholic hierarchy and the Bavarian political establishment. But Roth also paid a high price for his efforts. He was driven to suicide in 1960, in part because his bishop (who was, ironically, also a former Dachau prisoner) started using information from Roth’s Gestapo file to smear him as a homosexual.

More effective opposition to redeveloping the sites of Nazi concentration camps in the 1950s came from survivors' groups, who pressured and shamed the German authorities from outside. The Adenauer generation remained in control until at least the mid 1960s, but generational change began to swing in the survivors" favour a mere decade after the end of the war. By the mid-50s, those too young to have fought in the war were reading Anne Frank's diary and flocking to see the French film, Night and Fog. Again, it was predominantly the young who visited the Paulskirche in Frankfurt - as the seat of the Frankfurt parliament of 1848, it was also venerated as the cradle of German democracy - in order to view the exhibition about the mass murder of the Jews which accompanied the city's Auschwitz trial in the years 1963-5. Coming after the extraordinary publicity of the Eichmann trial in Jerusalem in 1960, this was a national event.

Faced with such mounting public pressure from within Germany as well as abroad, the Bavarian authorities were pushed into rehousing the ethnic Germans from the camp barracks and reconstructing the concentration camp at Dachau as a site of commemoration.

A visit to Dachau at any time since it was opened as a public memorial in 1965 would reveal a drab, sterile space built to last. Himmler's filthy, flimsy shanties of wooden barracks were finally torn down: hygiene provided a convenient pretext. In any case, Himmler had calculated during the 1937 expansion of Dachau that concentration camps would only be needed for another ten to fifteen years, and so the real barracks bad been far more temporary than the two which were rebuilt in commemoration. They met modem specifications with cement floors, tightly fitting windows and locking doors, the other thirty barracks simply mated with cement kerbstones. The mixture of gravel, grass, earth and cement which had covered the ground of the camp was resurfaced with light-coloured pebbles. Only the entry gate with its infamous sign - replicated at Auschwitz - "Arbeit macht frei", the watchtowers, the special prisoners' bunker and the two crematoria with their gas chamber were retained.

Gone were the canteen and infirmary, the punishment barracks and priests' chapel, the inmates' library; the brothel, greenhouses, the disinfection building, the kennels, the rabbit hutches, the SS prison, gone too were the SS slogans and murals. As Harold Marcuse notes in his most illuminating and intelligently argued study, this remodelling served to obliterate the starkly contradictory ways in which inmates devised stratagems to survive. The camp was streamlined according to the idealized images which Bavarian officials of the 1950s and early 60s retained of the concentration camps from Nazi photo-journalism of the time: "A barren, grey-white expanse surrounded by a high cement wall and watchtowers", it had, Marcuse suggests, "been reduced to a representation of the spotlessly ‘clean camp' of Nazi propaganda and its post-war mythic adherents".

The men who oversaw this project still belonged to that founding generation of the Federal Republic who had gone into rapid denial about the Nazi period and attempted to vilify survivors once again as "Communists", "criminals" and "asocials". Yet their vision was not to be the final one. As the generation of the 1968 student revolution came of age, successive exhibitions would be devised which concentrated on the suffering of the victims of Nazi terror, using enlarged photos of the inmates subjected to gruesome medical experiments, as emblematic of the atrocities inflicted there.

Marcuse has written a book which is at once a general political history of post-war West Germany's attitudes towards the Nazi period and a micro study of the way they were remade on one site, Dachau. Marcuse has organized his account of change around the notion of generational succession. He is scathingly critical of two generations in particular. As one might expect, he does not spare the Adenauer generation which strove so hard to forget and to obliterate the uncomfortable sides of the, Nazi heritage. But he does not forget to mention courageous individuals like the former camp prisoner Josef Müller, who made his career as a senior Christian Social Union politician and did all he could as a member of the Conservative Bavarian government to protect the Dachau site.

Part of the reason why concentration camp names like Dachau, Buchenwald, Bergen-Belsen, Ravensbrück and Sachsenhausen resonate so strongly in Western public consciousness - to the point where they are often confused with the death camps of the Holocaust - is because they have been preserved. As sites of memorial, of secular and religious pilgrimage and public education, they remain the physical loci of Nazi terror. None looks remotely like it did when in operation. Harold Marcuse's achievement, which he first fittingly worked out in a travelling exhibition on the history of monuments and memorials to the Nazi period, has been to unravel how and why that transformation took the form it did.