There were not enough British forces in India to contain the mutiny once it spread. And spread it did. The catalyst may have been the perceived cultural insensitivity of the introduction of the new rifle, but dissatisfaction with British rule kept the rebellion going.
Reinforcements were slow in coming. There was no telegraph in India so knowledge of the mutiny took a long time to reach Britain. There weren’t enough British troops in India to turn the tables on the mutineers until ships with reinforcements started arriving.
Those ships would have taken over a month and closer to two months before they berthed in Calcutta and discharged their troops. Add to that the time that it took for word to get out and it must have taken at least three months for reinforcements to arrive. It must have been a very long wait for the troops already there.
The mutiny started in April of 1857 and spread through that summer. It is not clear when the first troop ships arrived in India. In October George Welch embarked on the ship Defiance and by November he was in Calcutta. Other ships left and arrived at the same time. Reinforcements had arrived.
My drawing of the Defiance.
It is such an odd looking ship that it looks more like a floating arc.
Douglas, Althea. Time Traveller’s Handbook: A Guide to the Past. Dundern Press, Toronto, 2011
Holmes, Richard. Redcoat: The British Soldier in the Age of Horse and Musket. Harper Collins Publishers, London, 2001
Lewis-Stempel, John. The Autobiography of the British Soldier: From Agincourt to Basra, in His Own Words. Headline Publishing Group, London, 2007*
Ralby, Dr. Aaron. Atlas of Military History: An Illustrated Global Survey of Warfare from Antiquity to the Present Day. Parragon Books Ltd., Bath, UK, 2013