By Queen Victoria's Diamond Jubilee, the British Empire sprawled over five continents and hundreds of islands. It was by far the largest empire that had ever existed. The war of revenge against the dervishes - Salafis in the Sudan - culminated in the slaughter of Omdurman. Machine guns and artillery beat spears and muskets.
But signs of rot were already showing up. The turn of the twentieth century war against the Boers in South Africa was brutal, difficult, and was conducted ultimately with a policy of burning farms and imprisoning women and children in concentration camps, where poor food and sanitation killed tens of thousands. Of course this was a small scale slaughter compared to some previous colonial wars, but this time the victims, or many of them, were white Europeans. The peace would be a technical victory but mostly a loss.
Disgust with the conduct of the war combined with the well-founded suspicion that it had been fought for the benefit of a tiny number of rich people, above all Cecil Rhodes and the Rothschild banking family. The alliance of money and party politics in a whole pattern of colonial wars became better known.
Books were published showing, or purporting to show, that while the blood and taxes of ordinary citizens built and preserved the empire, the profits went overwhelmingly to a few bankers and their political dependents - a virtual who's who of British politicians including Gladstone, Disraeli, Randolph Churchill, Joseph Chamberlain and others.
Meanwhile, another symptom of Imperial insufficiency was felt. For a whole century Britain's rising GDP had outstripped the rest of Europe, but after 1870, Germany, with no empire to speak of, had been growing faster and had caught up with England in GDP, nearly equaled it's navy, and far outstripped it in the size of its Army.
(Based on Empire, by Niall Ferguson)