Why did the soldiers object to the use of new cartridges and muskets?

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What the Sepoys Thought

A century ago the British arrived in Hindostan and gradually entertained troops in their service, and became masters of every state. Our forefathers have always served them, and we also entered their service … By the mercy of God and with our assistance the British also conquered every place they liked, in which thousands of us, Hindostani men were sacrificed, but we never made any excuses or pretences nor revolted … But in the year eighteen fifty-seven the British issued an order that new cartridges and muskets which had arrived from England were to be issued; in the former of which the fats of cows and pigs were mixed; and also that attah of wheat mixed with powdered bones was to be eaten; and even distributed them in every Regiment of infantry, cavalry and artillery … They gave these cartridges to the sowars (mounted soldiers) of the 3rd Light Cavalry, and ordered them to bite them; the troopers objected to it, and said that they would never bite them, for if they did, their religion and faith would be destroyed … upon this the British officers paraded the men of the 3 Regiments and having prepared 1,400 English soldiers, and other Battalions of European troops and Horse Artillery, surrounded them, and placing six guns before each of the infantry regiments, loaded the guns with grape and made 84 new troopers prisoners, and put them in jail with irons on them … The reason that the sowars of the Cantonment were put into jail was that we should be frightened into biting the new cartridges. On this account, we and all our country-men, having united together, have fought the British for the preservation of our faith.