India would most likely be celebrating the 150th anniversary of its Independence not the anniversary of a failed mutiny if only the South and West had joined in instead of watching from the sidelines.
Writing in the Oxford History of Modern India, Percival Spears observes that:
The Madras and Bombay Presidencies were hardly touched by the Mutiny, whose areas of influence was the north and centre. The armies of the two presidencies were similarly almost free from the contagion.
Without siginificant reinforcements from outside, the British would have been hardpressed to control the vast land and contain the revolt if the fever of unrest had spread.
When you add in the apathy of the masses in most areas and lack of support from the Sikhs, the failure of the mutiny seems foreordained, in retrospect at least.
The Sikhs remained quiet and indeed actively helped in the operation [to quell the revolt]. They had nothing to gain from a revival of the Mughal power at Delhi; for them the memory of Aurangazeb and his immediate successors was even more bitter than that of Dalhousie.
While Spear is undoubtedly a biased writer, some of his observations ring true:
The passions of the mutineers were centered on their grievances, not on larger ideals. They knew what they disliked, but not what they would wish to set up in its stead. So they gained little advantage from successes and nothing but despair from their defeats.
Ultimately, the British put down the mutiny with a fury and resolution that won the admiration of many including that great American author Mark Twain.
After traveling widely through India and visiting some of the scenes of the mutiny in 1896, Twain wrote in Following the Equator: A journey Around the World:
The British were caught asleep and unprepared….but with English resolution and English devotion they…fought the most unpromising fight that one may read of in fiction or out of it and, and won it thoroughly.
The BBC web site has some rare pictures of the Mutiny.