Protesters formed 'a human chain' [=they stood next to each other with their arms linked] around the ancient tree to prevent it from being cut down.
In the United States, the President as the commander in chief is at the head of the military 'chain of command'.
I thought he really won the lottery but he was only 'pulling my chain'. [=he was only playing a joke on me]
(..) Well, I don't understand. We know it was. They were caught. They confessed. And they were executed. I know. And maybe that's really what happened. But I see this chain of events... ...these coincidences, and I have to ask: What if that isn't what happened? What if someone else unleashed that virus? (..)2005 V for Vendetta