More than 50 years ago, on 9 December 1971, PNS Hangor struck a heavy blow in the Arabian Sea.
The Pakistan Navy’s diesel-electric submarine detected an Indian task group off Diu and, in a precise attack, sank the frigate INS Khukri.
It was the first warship sunk in action by a submarine since World War II and remains India’s only warship lost in war.
PNS Hangor: the silent strike that reshaped the 1971 naval battle
Indian signals had warned of a submarine southwest of Diu.
Two Blackwood class frigates, INS Khukri and INS Kirpan, were sent to hunt it.
As evening fell on 9 December, Hangor gained contact.
A first homing torpedo, aimed at Kirpan, missed.
Khukri then closed in at low speed while testing sonar, against standard anti-submarine practice.
Commander Ahmed Tasnim fired again. The second torpedo hit INS Khukri under her oil tanks.
The ship went down within minutes, according to Pakistan’s account.
Kirpan counter attacked with mortars and later depth charges but failed to score.
Hangor fired a final torpedo at Kirpan, which the Indian frigate evaded before withdrawing.
The Pakistani submarine cleared the area and patrolled for days before returning safely to base.
The impact was immediate. The loss of INS Khukri shocked Indian planners and pushed parts of the fleet onto the defensive for the remainder of the war.
For Pakistan, the success showed what training, discipline and patience could achieve at sea even with fewer ships.
One boat, working quietly and methodically, changed the tempo of operations.
The legacy endures. PNS Hangor became a symbol of resolve for the Navy and a case study in how submarines can shape surface battles far beyond their size.
Each Independence Day, the story is retold as a reminder that vigilance and professionalism protect the coastline as surely as numbers and tonnage.
