India, Jan. 24 -- The standoff between the United States and Iran has heated up again after a short period when it seemed both countries were stepping back. That pause is now over. The situation has become tense and unpredictable once more.

This new crisis is closely linked to events that began in late December, when large protests inside Iran turned into one of the country's deadliest periods of internal unrest in recent years.

At the centre of the tension is a familiar pattern. The US is signalling it may use military force. Iran is warning that any attack even a limited one will be treated as an act of full war.

A US carrier strike group is now close to Iranian waters, and both sides are issuing open threats. To understand where thi...