Caucasian supremacy is believing that the Caucasian race is superior to that of non-Caucasian races. It is also the belief that everything good, civilized, & progressive originated with the Caucasian race. It is the premise that Caucasians have originated everything that was noteworthy. Such apologists assert that although civilization began in Africa, it is always delineated as North Africa. The Egyptians are always cited as Caucasians, never Africoid peoples. They refuse to acknowledge the contributions that non-Caucasoid people have made to civilization. While Europe was mostly a backwater in the Middle Ages, there were advanced civilizations in Asia & Africa such as China, Japan, Persia, Mali, & Songhai. Also remember, that the Mongols, an Asiatic race, conquered a large part of Europe. Please note that the Moors, an African people, conquered part of Southern Europe including Spain, creating a magnificent culture.
Europe was a very poor continent in the Middle Ages. When the age of exploration began, Europe started to become wealthy as a result of conquering/plundering resources from non-European continents-Asia, Africa, & the Americas. Not only were natural resources plundered, there were human resources which made Europe wealthy. This conquering resulted in the feeling of Caucasian supremacy. It was embedded in the Caucasian psyche that the non-Caucasian people they encountered were difference, hence inferior. Since previous Caucasian/European populations experienced poverty, they vow that they won't experience poverty again. So they enriched themselves at the expense of non-Caucasian nations & peoples.
Then there is the issue of so-called miscegenation. Caucasians are melanin recessive while non-Caucasians, particularly Africoids have graduations of melanin. Caucasians establish severe form of racial dominance/hegemony in order for them to at the top & continue to be in existence. Caucasians know that they would be wiped out if miscegenation continued on a wide scale. So racial categorizations were established, particularly in the United States. Caucasian apologists are fearful of more melanoid people such as Asians, Latinos, Natives, & particularly Africans. They want to retain their predominance because they are the ones who are THE TRUE MINORITIES in the world.