"The River War is a history of the British imperial involvement in the Sudan, and the Mahdi War between the British forces, led by Lord Kitchener, and the Dervish forces, led by Khalifa Abdallahi ibn Muhammad, 'The Mahdi,' heir to the self-proclaimed Mahdi Muhammad Ahmad who had embarked on a campaign to conquer Egypt, to drive out the non-Muslim infidels." (Source)
In the book, Churchill shares his first-hand and educated understanding of Islam. He wrote:
How dreadful are the curses which Mohammedanism lays on its votaries! Besides the fanatical frenzy, which is as dangerous in a man as hydrophobia in a dog, there is this fearful fatalistic apathy. The effects are apparent in many countries. Improvident habits, slovenly systems of agriculture, sluggish methods of commerce, and insecurity of property exist wherever the followers of the Prophet rule or live. A degraded sensualism deprives this life of its grace and refinement; the next of its dignity and sanctity. The fact that in Mohammedan law every woman must belong to some man as his absolute property — either as a child, a wife, or a concubine — must delay the final extinction of slavery until the faith of Islam has ceased to be a great power among men. Thousands become the brave and loyal soldiers of the Queen: all know how to die: but the influence of the religion paralyses the social development of those who follow it. No stronger retrograde force exists in the world. Far from being moribund, Mohammedanism is a militant and proselytizing faith. It has already spread throughout Central Africa, raising fearless warriors at every step; and were it not that Christianity is sheltered in the strong arms of science, the science against which it had vainly struggled, the civilisation of modern Europe might fall, as fell the civilisation of ancient Rome.