In the same way that the rotting carcasses of dead animals are breeding grounds for disease and pestilence. The rotting carcasses of failed cultures are the breeding ground of much of the worlds misery.

In a failed culture it is particularly difficult for young men to see that the life that their fathers tried to live is not available to them.  Some of them lash out, terror happens and then retribution.

What is a failed culture?  One that does not deliver health, opportunity and safety to its members as well as neighboring cultures deliver to these same benefits to theirs.

An actual cannon that was involved in two culture wars. 

The Spaniards against the Native Americans

and the Anglos against the Spaniards.  At the San Gabriel Mission.