I have just made a start on annotating the above poem for the New Reader's Guide, and find it somewhat baffling,  It's not very long, and one might say that its interpretation is, VERY broadly "Mother [= England], you can trust us, your sons [= Canada, Australia, NZ. etc.] 
Durand states that the words in line 3 "From the whine of a dying man, from the snarl of a wolf-pack freed" refer to the Liberal leader W E Gladstone, and to the Irish Nationalist party.  If that is so, then it does not chime with the events of the period.  One might say that Gladstone and the Irish Nationalists were at the peak of their power at the time the poem was first published.  Gladstone had steered the Second Irish Home Rule bill through its Second Reading in April 1893, and the poem was published in May 1893.  It was presumably being written sometime between late 1892 and March/April 1893, while the bill was before Parliament.  The bill was highly contentious, and its passage through the House of Commons must have been at best uncertain when the poem was being written.  If RK thought that Gladstone's influence and the power of the Irish Nats was on the wane, he was either guessing wildly (and incorrectly, since the bill passed almost as he was writing the poem), or else he was being uncannily prescient, since the bill was heavily defeated in the House of Lords some six months later, and Gladstone resigned the next year (over another matter).
Can anyone help to elucidate, please?
Alastair Wilson