Some Indians came to believe that the British intended to convert them either by force or by deception (for example by causing them to lose caste) to Christianity. The British religious fashion of the time was Evangelism, and many East India Company officers took it upon themselves to try to convert their Sepoys. The Doctrine of Lapse, part of the British policy of expansionism, was also greatly resented. If a feudal ruler did not leave a male heir through natural process, i.e. his own child, not an adopted one, the land became the property of the British East India Company. Nobility, feudal landholders, and royal armies found themselves unemployed and humiliated. Indians were unhappy with the draconian rule of the British which had embarked on a project of rather rapid expansion and westernisation, that were imposed without any regard for historical subtleties in Indian society.
Anger due to social reform by the British
Some Indians were unhappy with the rule of the British and perceived a project of westernisation to be taking place, that, however well-meaning they may have been, they believed were imposed without any regard for Indian tradition or culture. The outlawing of Sati (self-immolation by widows) and child marriage, which to some appeared to be a precursor to an imposition of Christianity, has also been put forward as a reason for the revolt.
The British East India Company was a massive export company that was the force behind much of the colonization of India. The power of the Company took nearly 150 years to build. By 1857, the last vestiges of independent Indian states had disappeared and the Company exported untold quantities of gold, jewels, silver, silk, cotton, and a host of other precious materials back to England every year. The land was reorganised under the comparatively harsh Zamindari system to facilitate the collection of taxes. In certain areas farmers were forced to switch from subsistence farming to commercial crops such as indigo, jute, coffee and tea. This resulted in hardship to the farmers and increases in food prices. Local industry, specifically the famous weavers of Bengal and elsewhere, also suffered under British rule. Import tariffs were kept low, according to traditional British free-market sentiments, and thus the Indian market was flooded with cheap clothing from Britain. Master weavers even had their fingers cut off to prevent them from weaving.
The Enfield Rifle
The rebellion was, literally, started over a gun. Sepoys throughout India were issued with a new rifle, the Pattern 1853 Enfield rifled musket. To load both the old musket and the new rifle, soldiers had to bite the cartridge open and pour the gunpowder it contained into the rifle's muzzle, then stuff the cartridge case, which was typically paper coated with some kind of grease to make it waterproof, into the musket as wadding, before loading it with a ball. It was believed that the cartridges that were standard issue with this rifle were greased with lard (pork fat) which was regarded as unclean by Muslims, or tallow (beef fat), regarded as sacred to Hindus.
Prophecies, omens, signs and rumours
Another rumour that spread was an old prophecy that the Company's rule would end after a hundred years. Their rule in India had begun with the Battle of Plassey in 1757. Chapaties and Lotus Flowers began to circulate around large parts of India, quoting the famous line "Sub lal hogea hai." (Everything has become Red.), passed around by people from town to town and village to village, as a symbol of the prophecy and a sign of the coming revolt. It was also a common belief in the decade after the rebellion, commented on in the British and colonial press, that either the Persians, Chinese, Jews or Russians had directly or indirectly influenced the sepoys to revolt.