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]
(..) beginning with the attack on the USS Kelvin, culminating with the events of today, thereby creating an entire new chain of incidents... that cannot be anticipated by either party. An alternate reality. Precisely. Whatever our lives might have been (..)2009 Star Trek