Eric Posner, professor of law at the University of Chicago, in the NYT (April 28, 2004):

The decision by the Coalition Provisional Authority to ease its policy barring former Baath Party members from Iraqi government jobs has generated widespread criticism in Iraqi political circles. Ahmed Chalabi, America's onetime favorite member of the Iraqi Governing Council, said that giving jobs to former Baathists was like "allowing Nazis into the German government immediately after World War II." But that's precisely the point — the history of the last 50 years shows that countries trying to make transitions to democracy must inevitably bring back at least some members of the ousted regime.

After World War II, the allies resolved not only to punish Nazi war criminals but also to purge Nazism from German public life. Yet even before the Nuremberg trials had concluded, the Americans realized that they could not rebuild Germany without the help of at least some former Nazis who had dominated the bureaucracy, industry and the military. Although the worst Nazis were punished, most others were eventually given amnesty and went to work on reconstruction.

Simultaneously in Japan, transitional justice was even more perfunctory. From the beginning, the Americans decided that Emperor Hirohito would have to be retained so that the United States could exert control over the populace through him. His absence from the Tokyo trials of war leaders weakened that tribunal's impact, and soon enough many members of the wartime regime were allowed to help get the country back on its feet.

In both cases, the decisions to ease the purges were partly, but not entirely, realpolitik. Yes, America needed Germany and Japan as allies against the Soviet Union. But it also realized that neither place could become a functioning liberal democracy without the cooperation and expertise of the vast majority of those tainted by the previous governments. An endless occupation was not an attractive prospect — just as it is not in Iraq now. The compromise in both Germany and Japan was a series of high-profile trials of the worst war criminals, followed by amnesty for most everyone else, many of whom were not only complicit in the old regime but responsible for some of its ugliest decisions.

This set the pattern for the next several decades — in Spain, Greece, Portugal, Argentina, Chile, Hungary, Czechoslovakia, Poland, the former East Germany, the Philippines, South Africa and elsewhere. Although in some cases moderate transitional justice measures were carried out — including truth commissions, reparations, purges of leaders and collaborators, and trials of some lower-level officials like border guards — most holdovers from the old regime were permitted to take part in the new.