Complex sentence: The flashpoint of the rebellion was the introduction of the Enfield rifle; the cartridges for this weapon were believed to be greased with a mixture of beef and pork fat, which was felt would defile both Hindu and Muslim Indian soldiers.
Split into simpler sentences: The flashpoint of the rebellion was the introduction of the Enfield rifle. The cartridges for this weapon were believed to be greased with a mixture of beef and pork fat, which would defile both Hindu and Muslim Indian soldiers.