Because it was the first time in history that humans (Nazis) performed a genocide on over 6.5 million Jews (including gypsies, Polish and anyone who fought against the Nazi order.)
Presumably, the question means unique in a way other than happening to specific people at a given time in a particular region. In other words, I assume it means something like: Has anything similar happened to other groups, especially peoples?
If that is what's meant, I would say Yes, there have been comparable genocides. The most obviously compable genocide is that of the Armenians by the Ottoman Turkish government in 1915-1917 (continued in 1922).
Unfortunately, there have been genocides throughout human history, including ones that were more successful in wiping out their target.
However, what makes the Holocaust unique is that it was the first (and, thankfully, so far the only) case where the full institutional effort of an industrialized nation was put to the purpose of genocide.
Genocide in human history has been a haphazard affair. Often, while it was the official policy of a government or ruler to kill certain groups, the actual task of performing that action was seldom organized. It such a policy had never before become an institutionalized part of a government. That is, the uniqueness of the Holocaust is that the genocide policy was not just decided upon, but incorporated into the actual German nation's government, in the same manner as one would have a Department of Transportation or similar formal structure.
The Holocaust harnessed the innovations of industrial organization as pertains to government, and used that organization to carry out a genocide in an ultra-efficient manner never before seen. The terror of the Holocaust is that such efficiency of mass-murder is possible, when using the very organs of the state itself to carry it out.
To be explicit: the uniqueness of the Nazi Holocaust is that it harnessed the organizational and mechanical innovations of the Industrial Revolution to genocide into a institutionalized, formalized, planned, and executed government bureaucracy. The Holocaust's "product" was Death: designed, regulated, planned, manufactured, mass-produced, and sold to its victims using all the advancements of the Industrial Revolution.
The Horror of this industrialization and efficiency was that it required relatively little effort and materials to accomplish mass murder. Total estimates of the number of people (primarily SS) actually involved directly in the Holocaust is only a few thousand. The mechanization and organization of the Holocaust meant that those few thousand people were able to exterminate over a thousand times their number of victims in a couple of years. This works out to a single SS (or other perpetrator) being able to effictively kill several hundred people per year by working in the extermination system. This meant that the Holocaust required a relatively small portion of the country to participate (something far easier to accomplish than getting a large portion of the army or population involved), it was far easier to hide that it was occuring, and the killings could continue for very extended time periods, all of which are radically different than any other genocide in human history.
The ISBN of Is the Holocaust Unique? is 0813336864.
what makes the mantle unique
They are unique by being unique.
because it is unique
Asking what makes Sony unique is a little like asking what makes YOU unique. They are one of a kind; there is no other 'Sony' "There can be only one"!
It's the Saturn rings that makes this planet unique.
What makes it unique is it is the first planet in the universe and it is the closest to the sun.
0.1% of are DNA makes us unique.
It's plants, animals, and weather makes it unique
it makes it unique because it is only for a sertain animal and will survive for that animal only What makes a habitat unique, is the animal that resides there. The habitat makes it possible for that organism to survive and thrive.
what makes angola unique
everything about Tonga is unique
There is nothing that makes any individual unique.
Its all their perfect understanding of the market which makes them so popular and unique.
There is remembrance of the Holocaust but there is no 'Holocaust movement'. That expression makes it sound like a political campaign.
in an atom protone makes the each element unique
What makes a portugese man of war unique is its shape
it is not unique in any way
Meteors are unique by having humans
it is unique because its staety sturdy
There are a few facts that make Massachusetts unique. Some of the things that makes this state unique are the river, mountains and the history of the state.
The Holocaust suggested that earlier ideas about progress were not true. The Holocaust makes one consider that postmodernism is wrong as much to do with the Holocaust is with the absence of empirical data.
What makes earth unique in its ability to sustain life
A person's own experiences make it unique.
The Romanian government has nothing unique.