Nineteenth-century imperialists claimed they were fulfilling a "civilizing mission" in their overseas conquests. to what extent was this claim true? how was this claim ideologically supported by scientific racism?  

The imperialist claims that they colonize other nations to help them develop and civilize the non-civilize tribes and people. It also the destiny of the West to conquer and teach this people and to spread Christianity all over the world. One concrete example of this is the poem The White Man's Burden of Rudyard Kipling to justify colonialism. Also they believed that their superior race should lead the lesser people to development.

It’s a and your welcome