In the poem "The White Man's Burden" by Rudyard Kipling what is the actual "burden" that white men are plagued with?

According to the poem, the actual burden that white people
are plagued with is the non-white people that they have conquered and the need to care
for these non-white, inferior peoples.

What Kipling is
saying is that when a white country colonizes, it has all these people who are "half
devil and half child."  It must, therefore, care for the those people the same way that
a parent must care for its children.

Parenting clearly
involves sacrifice and so, says Kipling, does colonization.  White people will have to
go out to all these primitive places where they have to do without civilized comforts
and work hard (in "heavy harness") to take care of all these inferior people who need to
be helped because they are not advanced enough to take care of
themselves.