During the Indo-Pakistani War of 1971, Indian Osa-class boats raided the port of Karachi in two highly successful operations causing severe damage and sinking several ships with their P-15s, among them the destroyer, Khaibar.
She was a former Battle-class destroyer, originally designed as an anti-aircraft ship.
Her armament might be effective against conventional air threats, (mounting 5 × 114mm guns and several 40mm Bofors), but had little chance against anti-ship missiles.

These raids were meant to strike Karachi and destroy the Pakistani Navy in Western Pakistan.
The first action, Operation Trident, was carried out by three Osa class missile boats on the night of 5 December . '
Operation Trident' involved:
INS Nipat (Lt.-Cdr B.N Kavina, VrC)
INS Nirghat (Lt.-Cdr I.J Sharma, AVSM, VrC)
INS Veer (Lt.-Cdr O.P Mehta, VrC, NM)
Around 20:30, a target was acquired by radar, at a distance of over 40 miles (64 km), and Nirghat fired two missiles.
This target was the destroyer Khaibar, sailing at 20 knots (37 km/h).
The crew of the ship saw a "bright light" in the sky, low on the water.
Believing it to be the afterburner of a fighter aircraft, Khaibar opened fire with her Bofors guns, but these were not effective against such a small, fast target.
The missile struck the starboard side at 22:45, destroying the electrical system.
One of the boilers, possibly struck by the HEAT charge, also exploded.
Despite thick smoke and a fire, Khaibar was still able to engage the second missile, again mistaking it for an enemy fighter.
This missile struck the ship four minutes after the first, destroying and quickly sinking her.

During this action, Nipat attacked another two ships; the cargo vessel Venus Challenger, which was carrying ammunition from Saigon, was destroyed.
Her escort, the destroyer PNS Shahjahan was severely damaged and later scrapped.

Veer then attacked Muhafiz at 23:05, (she was a minesweeper that had witnessed the attacks against Khaibar); she was hit and disintegrated, throwing most of the crew into the water before she sank.

Nipat fired two missiles at the port of Karachi.
This is the first known use of an anti-ship missile against land targets.
Large oil tanks, identified by radar, were hit by the first missile, destroying it, while the second weapon failed.
Over the following nights there were other ship actions.
Karachi was again attacked with missiles, while Petja-class frigates provided anti-submarine protection to the Osa-class boats.

On the night of 8 December, in the second operation, Operation Python, the Osa-class boat Vinash, escorted by two frigates, fired missiles at Karachi in a six-minute action.
One missile hit an oil tank, destroying it.
The British ship Harmattan was sunk, the Panamanian ship Gulfstar was set on fire.
The Pakistan Navy fleet tanker, PNS Dacca, was badly damaged and only survived because the commanding officer, Captain.
S.Q. Raza S.J. P.N., ordered the release of steam in the pipes that prevented the fire reaching the tanks.
Though anti-aircraft guns opened fire in response, they only managed to hit a Greek ship, Zoë, that was moored in the port and consequently sank.

In all these actions against large ships, the P-15 proved to be an effective weapon, with a devastating warhead.
Out of eleven missiles fired, only one malfunctioned, giving a 91% success rate.
This gave every Osa FAC the possibility of striking several targets.
Big ships, without any specialized defence, were targets for P-15s.
During the Indo-Pakistani War of 1971, Indian Osa-class boats raided the port of Karachi in two highly successful operations causing severe damage and sinking several ships with their P-15s, among them the destroyer, Khaibar. She was a former Battle-class destroyer, originally designed as an anti-aircraft ship. Her armament might be effective against conventional air threats, (mounting 5 × 114mm guns and several 40mm Bofors), but had little chance against anti-ship missiles.
These raids were meant to strike Karachi and destroy the Pakistani Navy in Western Pakistan. The first action, Operation Trident, was carried out by three Osa class missile boats on the night of 5 December . 'Operation Trident' involved:
INS Nipat (Lt.-Cdr B.N Kavina, VrC)
INS Nirghat (Lt.-Cdr I.J Sharma, AVSM, VrC)
INS Veer (Lt.-Cdr O.P Mehta, VrC, NM)
Around 20:30, a target was acquired by radar, at a distance of over 40 miles (64 km), and Nirghat fired two missiles. This target was the destroyer Khaibar, sailing at 20 knots (37 km/h). The crew of the ship saw a "bright light" in the sky, low on the water. Believing it to be the afterburner of a fighter aircraft, Khaibar opened fire with her Bofors guns, but these were not effective against such a small, fast target. The missile struck the starboard side at 22:45, destroying the electrical system. One of the boilers, possibly struck by the HEAT charge, also exploded. Despite thick smoke and a fire, Khaibar was still able to engage the second missile, again mistaking it for an enemy fighter. This missile struck the ship four minutes after the first, destroying and quickly sinking her.
During this action, Nipat attacked another two ships; the cargo vessel Venus Challenger, which was carrying ammunition from Saigon, was destroyed. Her escort, the destroyer PNS Shahjahan was severely damaged and later scrapped.
Veer then attacked Muhafiz at 23:05, (she was a minesweeper that had witnessed the attacks against Khaibar); she was hit and disintegrated, throwing most of the crew into the water before she sank.
Nipat fired two missiles at the port of Karachi. This is the first known use of an anti-ship missile against land targets. Large oil tanks, identified by radar, were hit by the first missile, destroying it, while the second weapon failed. Over the following nights there were other ship actions. Karachi was again attacked with missiles, while Petja-class frigates provided anti-submarine protection to the Osa-class boats.
On the night of 8 December, in the second operation, Operation Python, the Osa-class boat Vinash, escorted by two frigates, fired missiles at Karachi in a six-minute action. One missile hit an oil tank, destroying it. The British ship Harmattan was sunk, the Panamanian ship Gulfstar was set on fire. The Pakistan Navy fleet tanker, PNS Dacca, was badly damaged and only survived because the commanding officer, Captain. S.Q. Raza S.J. P.N., ordered the release of steam in the pipes that prevented the fire reaching the tanks. Though anti-aircraft guns opened fire in response, they only managed to hit a Greek ship, Zoë, that was moored in the port and consequently sank.
In all these actions against large ships, the P-15 proved to be an effective weapon, with a devastating warhead. Out of eleven missiles fired, only one malfunctioned, giving a 91% success rate. This gave every Osa FAC the possibility of striking several targets. Big ships, without any specialized defence, were targets for P-15s.
P-15 Termit