'Cauldron' was a British special forces undertaking within 'Jubilee', which included two such undertakings (19 August 1942).
'Cauldron' was the attack of Lieutenant Colonel the Lord Lovat’s No. 4 Commando, including 50 US Army Rangers, against the 'Hess' batteries of German heavy artillery at Quiberville and Varengeville on the western flank of the main assault on Dieppe on the northern coast of German-occupied France. No. 4 Commando achieved the only clear-cut success of the landings, attacking a battery of six 150-mm (5.91-in) guns immediately to the west of Varengeville sur Mer.
Lovat divided his force into two and his second in command, Major Derek Mills-Roberts, landed with 88 men on Orange 1 beach and then engaged the battery with small arms and mortar fire from a wood at a range of some 3,000 yards (2740 m). Lovat took the remainder of his men across Orange 2 beach farther to the west, whence they proceeded inland before swinging first to the south-east and then to the north-east to attack the battery from the rear. A fighting patrol cut the communication lines from a German observation post in a lighthouse. Both the main groups suffered casualties as they got into position.
Supermarine Spitfire single-engined fighters of No. 129 Squadron strafed the battery while Mills-Roberts laid down an intensive machine gun barrage and fired smoke from his 2-in (51-mm) mortars. Lovat fired a series of white Very lights and when Mills-Roberts stopped firing, the commandos charged, destroyed the guns and finally withdrew successfully.
The other special forces undertaking was committed on the eastern flank of the main assault, and involved Lieutenant Colonel John Durnford-Slater’s No. 3 Commando, which was carried in 25 LCVPs and was to make two landings some 8 miles (13 km) to the east of Dieppe with the task of silencing the coastal battery near Berneval. The guns of this battery could fire on the landing at Dieppe some 4 miles (6.4 km) to the west, so the three 170-mm (6.69-in) and four 105-mm (4.13-in) guns of the 2/770th Batterie had to be taken out of action by the time the main force approached the main beach.
The craft carrying No. 3 Commando, approaching the coast to the east, were not warned of the approach of a German coastal convoy that had been located by British 'Chain Home' radar stations at 21.30. S-boote escorting a German tanker torpedoed some of the landing craft and disabled the escorting gunboat SGB-5. ML-346 and LCF-1 then combined to drive off the German boats, but the assault group was dispersed, with some losses, and the German coastal defences were alerted.
Only 18 commandos managed to land at the right place, and reached the perimeter of the battery via Berneval before engaging the target with small arms fire. Although unable to destroy the guns, the commandos were able with their sniping to distract the battery for a time, to such good effect that the gunners fired wildly and managed to sink none of the assault convoy ships off Dieppe. The commandos were eventually forced to withdraw in the face of superior German forces.