The Cristeros Rebellion took place in Mexico between 1926 and 1929 in response to increasing persecution of the Church by the government of Plutarco Elias Calles. You can read more about it at the Wikipedia article Cristero War.
I came across this fascinating video via Hallowed Ground. It includes interviews with those who were involved at the time.
The video highlights some of the many atrocities of the Government forces and the execution of innocent civilians. I am aware also of the conduct of the Cristeros in some instances, for example the burning of a train carrying civilians. However, there are some inspiring stories of the genuine martyrs of this period, including Fr Miguel Pro (left)and the 14 year old Jose Sanchez del Rio.