Actually it was written about the River War, the campaign by the British against the Mahdi army, a crowd exactly similar to ISIS today. Back then of course the West wasn’t so squeamish about dealing with crazy jihadis.
At the battle of Omdurman the British wiped out the Mahdi army, cheerfully spraying them with Maxim gunfire and artillery. The Mahdis lost 10,000 dead (Churchill personally dispatched a couple of them), 13,000 injured and 5,000 prisoners, the Brits lost 47 dead.
It worked a treat, funny how no one seems willing to do something similar these days.
Ah, yes, 1899. Didn’t some Brit politician get arrested this year for reading this passage aloud in public?