Pakistan, June 2 -- There is a river that has flowed through the heart of Pakistani Punjab for centuries. Farmers along its banks have measured their seasons by it, calibrated their sowing to it, and built civilisations around the certainty of its arrival.

The Chenab is not merely a river to Pakistan. It is a lifeline. And for the first time in modern history, that lifeline has an adversary with both the intent and the infrastructure to control it.

India's decision to fast-track construction of the Chenab-Beas Link Tunnel - an 8.7-kilometre underground conduit designed to divert waters from the Chandra River, a Chenab tributary in Himachal Pradesh, through the Pir Panjal mountain range into the Beas basin - has sent a tremor through Isl...