'Parole' was the British passage of the OS.33 convoy from Liverpool, UK, to Freetown, Sierra Leone (1/20 July 1942).

During this operation, the 'Hai' (i) wolfpack inflicted considerable losses on vessels which had straggled or detached from the main convoy in mid-Atlantic.

The OS.33 convoy departed Liverpool at 16.05 on 1 July with 20 merchant vessels in line down the Mersey river estuary to the end of the swept channel. The ships then proceeded two abreast until eventually, when joined by eight vessels from Milford Have, nine from the Clyde river and five from Oban, they formed the full nine columns of four or five ships which was the designated convoy formation. In all, 40 merchant vessels, 10 of them carrying dangerous cargoes, and one oiler steamed round the north of Ireland bound for the South Atlantic. The convoy commodore (Rear Admiral Sir Oswald Dawson) sailed in the 6,601-ton British Castalia, the leading vessel of the central column, for Freetown and thence Bombay with a general cargo and 50 passengers, while the masters of the 6,568-ton British New Texas and 6,568-ton British New Toronto, each carrying stores, acted as the vice commodore ands rear commodore respectively for Takoradi. The convoy included one oiler, the 7,347-ton British Laurelwood, to refuel the 15 escort vessels.

In the event of any ship being damaged while in the convoy, the rear ships of the columns were designated as rescue ships with instructions to rescue survivors and then rejoin the convoy. The ships were instructed to maintain a distance of 3 cables (200 yards) by day and 5 cables (1,000 yards) by night between the columns and 2 cables (400 yards) from the vessel in front. These distances were obtained by sextant angle from neighbouring vessels' mastheads, whose heights were noted on the Cruising Order. The normal cruising speed was 8 kt.

The Liverpool contingent had been at sea for only 150 minutes before the armed trawler Ophelia, which was not connected with the convoy, was in collision with the 7,173-ton British Ocean Honour and returned to Liverpool for repairs. The merchant vessel, which was carrying stores and bound eventually for the Middle East, suffered only minor damage above the waterline and continued with the convoy.

The passage to the Azores islands group was uneventful except that on 10 July the 7,524-ton British Empire Attendant, carrying stores, finally lost contact with the convoy after breaking down for the seventh time, and was torpedoed by Kapitänleutnant Werner Schulte’s U-582 on 15 July with the loss of all hands.

At 09.00 on 11 July the British vessels bound for South America (4,284-ton Shaftesbury carrying coal, 4,764-ton Radcombe carrying coal, 6,723-ton Sithonia carrying coal, 5,335-ton Bruyere carrying general cargo, 7,073-ton Cortona carrying general cargo and 5,242-ton Siris carrying general cargo) and the ships bound for South Africa (4,847-ton British Consuelo carrying general cargo, 10,735-ton British Port Hunter carrying stores and seven passengers, 9,461-ton British Glenberg carrying stores and 24 passengers eventually for the Persian Gulf, 5,011-ton British Dona Aurora carrying stores, 5,184-ton Norwegian Sophocles carrying stores and 4,890-ton British Marsdale carrying stores and 20 passengers) were detached from the convoy to proceed independently.

It was not until 15.34 on 11 July that the Admiralty sent a signal to the convoy that it had picked up a radio signal from a U-boat at 12.58 giving a sighting report of the convoy. This report came too late for the vessels which had already been detached, and nearly half of these were torpedoed and sunk. The ships which were sunk were Cortona, which was damaged by Korvettenkapitän Werner von Schmidt’s U-116 on 12 July and sunk later on the same day by Kapitänleutnant Adalbert Schnee’s U-201, Port Hunter sunk by Schulte’s U-582 on 12 July, Siris sunk by U-201 on 12 July, Shaftesbury sunk by U-116 on 12 July, Sithonia sunk by U-201 on 13 July, and Empire Attendant by U-582 on 15 July.

The arrival of the convoy at Freetown was signalled at 13.13 on 20 July.

The escort originally detailed for the OS.33 convoy comprised the sloops Pelican, Erne and Lowestoft, and the frigates Spey and Rother, but the HF/DF-equipped Erne did not sail as she lacked sufficient training and was therefore not considered to be efficient. Two Free French vessels, the destroyer Léopard from Greenock and minesweeping sloop Commandant Duboc from Londonderry, were ordered to accompany the convoy to Freetown in part as additional support but also to obtain data on their endurance figures and fuel consumption at economical speed.

The escorts performed well in the escort protection role, and the convoy lost no ships while under their protection. For example, the formation reported on 11 July was Léopard and Pelican 8 miles (13 km) and 2.25 miles (3.67 km) ahead of the convoy respectively, Spey and Rother 8 miles (13 km) miles on the port and starboard beam respectively, and Lowestoft and Commandant Duboc 2.9 miles (4.67 km) on the port and starboard bow respectively.

On 12 July Léopard collided with Lowestoft causing serious damage: Lowestoft was holed in the forward boiler room so badly that the main engine was unworkable and the ship also lost her funnel. Léopard, with only 2.5 days of fuel remaining, took Lowestoft in tow and made for the Azores islands group for rebunkering of the French ship and emergency repairs for the British ship.

The corvette Jonquil was then ordered to provide additional support and joined the escort on 14 July. Also, the destroyers Penn and Quentin were ordered to rendezvous with the convoy and arrived on 15 July, so the convoy remained well protected.

A number of attacks were carried out on the U-boats between 11 and 14 July, but only the only one to gain success was that of 11 July by Pelican, which sank Kapitänleutnant Heinrich Zimmermann’s U-136.