The military causes of Sepoy Mutiny primarily led to the outbreak of the 1857 revolt. During 1857 there was a lot of discontentment among the Indian soldiers. The highest pay attainable by a sepoy as Subedar of the infantry was less than the minimum pay of a raw European recruit. Very often there was no promotion for an Indian soldier. The case was so that an Indian soldier joined as a Risaldar and also retired as a Risaldar. The Government did not trust the Indian soldiers. The self-respect of the soldiers was trampled upon at every step.

The number of British troops in India was never very large but the English Company was able to recruit without trouble from the native Indians. With the British in ratio of one in four thousand, the ratio of the troops had been fixed by a former Governor-General as one British soldier to three native soldiers and had never been less than one to four. Originally, the native soldiers were low cost Afghan or Turkish mercenaries. With a view to make the army more national, the sons of the landowners and peasants were deliberately recruited. In the army of Bengal, three-fifths of the men serving in the 63 Infantry Regiments came from Avadh. They enjoyed several privileges which disappeared after the annexation of Avadh in 1856. When they went home, they were treated with contempt as the slaves of the British.

It is true that the native soldiers seemed to be loyal to the British but there had been previous instances of trouble among them. In 1806, there was a mutiny of the native soldiers at Vellore. In 1824, a regiment which was ordered to go to Burma defied the orders on account of the dispute over cooking pots. In 1852, the 38th Native Infantry refused to cross the sea to Burma. However, in 1856, the General Service Enlistment Act was passed to give the authorities absolute power to take the soldiers out of India. This was very much resented as the new law was to apply to all the future entrants to the army which was considered to be a monopoly of a class of people in the country.

The increased ratio of Indian troops to British troops gave a sense of self-confidence to the Indian troops. There were small mutinies or near -mutinies at different places. There were signs of hatred between the white and coloured people. Almost all of them were caused by the fear that the British were trying to break caste and convert the sepoys to Christianity.

Rumours started circulating among the native soldiers. It was rumoured that all the armies of the Company had been killed in Burma and all the British in the Crimean War. It was said that English women were to be brought to India to marry Indian Princess whose children would then become Christians and all sepoys would be baptised. There was to be a mass murder of sepoys by a mine under the parade ground. The British had polluted sugar and mixed ground bullock's bones with flour and the sepoys were forced to eat cow's flesh. Although the government heard all these rumours they did nothing to stop them. Ignoring the fact that Indian soldiers regarded services in the form of trade guild, the Indian officers continued to disregard their customs and religions.

Although outwardly all seemed to be calm, below the surface there was a highly inflammable situation and some common cause was required to unite the different religions against the British and that was provided by the introduction of the greased cartridges.