When he issues his command to "fill the mouth of famine/half devil and half child," Kipling speaks to Americans and refers to the native people of the Philippines, who were both primitive and lacking in knowledge.
Originally, Kipling composed his poem for the Diamond Jubilee of Queen Victoria, but he decided instead upon another poem, "Recessional." Then, Kipling altered the text of "Burden" to allude to the American colonization of the Philippines, which the United States had acquired after winning the Spanish-American War, and to warn the U.S. of the dangers of colonization.
Within the context of Kipling's time (1899), the Victorian Age when the "sun never set on the British Empire," England was the greatest of imperial powers, and the country took pride in its accomplishments of bringing civilization to foreign and uncultured lands. As an Englishman, and the son of parents who were part of this colonization in India where he was born, Kipling would likely have shared this pride in imperialism. Yet, because he loved the Indian people, he perceived both what he termed "the white man's burden" of trying to bring indigenous peoples to the level of civilization at which European countries were and the negative effects, as well, on both races as many English died in the efforts of colonialism and many conquered people resented the conquerors for having invaded their land and suddenly imposed a new way of life upon them.
Take up the White Man's burden-- Send forth the best ye breed-- Go bind your sons to exile
To serve your captives' need;
To wait in heavy harness,
On fluttered folk and wild--
Your new-caught, sullen peoples,
Half-devil and half-child.
In Kipling's time there was a widespread belief among Europeans that they must bring Christianity to the primitive people of foreign lands, those that were "half-devil" and that they must bring literacy and education and social advancements, as well to those that were "half-child." Thus, the "White Man's burden" is his obligation to native peoples.
But, there were Americans who disagreed and took Kipling's warning. One U.S. senator, Benjamin Tillman, read three stanzas from Kipling's poem on the floor of the Senate as part of his argument that America should relinquish its claim to the Philippines. Tillman argued,
"Why are we bent on forcing upon these people a civilization not suited to them and which only means in their view degradation and a loss of self-respect, which is worse than the loss of life itself?"
Additional Source: Stephen Greenblatt (ed.), Norton Anthology of English Literature, New York 2006