How did the introduction of Enfield Rifles become an immediate cause of the War of Independence in 1857?

The immediate cause of the War of Independence was the introduction of Enfield rifles in place of the old iron made Brown Bess Guns. The cartridges to be used for the Enfield rifles were greased with the fat of cows and pigs. The cow is sacred for the Hindus and the Muslims consider pigs as unclean. The loading process of the Enfield rifle involved bringing the cartridge to the mouth and biting off the top greased paper with the teeth. The information about the greased cartridges spread like wild fire. The whole Bengal army was seized with panic. The soldiers refused to use these cartridges and staged an uprising when they were forced to use them.