It is one of the "bracket poems" to "Brother Square-Toes" in Rewards and Fairies, one of Kipling's two 'children's books' about English history that are really not for children at all (he said as much in a letter to IIRC Cecil Rhodes.)
Kipling often "bracketed" his short stories with two poems that would introduce and sum up the short story.
If you read "Brother Square-Toes" you will see that it is about George Washington making hard decisions on behalf of the fledgling American government . . . after a dreadful confrontation with nay-sayers in his own cabinet, he tells Cornplanter, "My brothers know it is not easy to be a Chief."
On reflection, maybe even closer to President Bush than we thought. Somebody ought to send him the story to go with the poem (I'm sure people have sent him the poem alone!)
thank you so much for further information on the poem. I had no idea.