Are all terrorists together in one location what many might call an army and an identifiable target and is it why they exist as cells?

Terrorists are spread throughout the world and are easiy recruited/exploited via social media. Witness today's killing at OSU by one demented individual who thought he was serving Allah.

Definitely yes. Being spread out in small groups makes the enemy harder to identify, enables them to practice guerilla warfare as well as terrorism , and use civilians as sheilds. Small units arranged in pyramid hierarchy, like spy organizations, protect all other cells if one is discovered or taken out. This strategy makes a terrorist state particularly difficult to defeat. But not impossible, and the best minds have already developed the means and are starting to apply them.

ISIS has no idea of the real power of the combined forces of the West. In the end, they will have no chance of winning or surviving.