The Mark 'Na75' was allocated to 200 plus Churchill Mark IVs that had their main armament, the 6-pounder, replaced by 75mm guns taken from knocked out Shermans. The American guns were installed at the REME Workshops, Bône, Algeria, under the direction of Captain (later Major) Percy Hulme Morrell, M.B.E.

As the Na75 only saw service in Italy, the North Irish Horse being the first unit to receive them in July 1944, the purpose of this article is twofold:
1. To take extracts from David Morrell's account of his father's work to cover, and comment on, the raison d’etre for the conversion, and the work entailed for so doing. The intention of the comments is not to belittle the splendid work he and his crew performed at Bône, rather than to point out that his impressions of Churchill performance in Tunisia originate only from 21st Tank Brigade's brief time in action - perhaps it is due to his unit and the 21st Tank Brigade both being part of 1st Infantry (Mixed) Division, the only one of the ill-conceived 'Mixed' divisions that saw action, albeit just for a few days longer than one month.
2. The role Na75s played.

"The Background Raison d’etre
The 21st and 25th Tank Brigades, which were incidentally, the first two brigades in the British Army to be equipped 100% with Churchill tanks, took a pretty severe beating in the battles which led up to the fall of Tunis. 1 In fact it was apparent that the Churchill was anything but an unqualified success. It was heavy and well armored, and had many of the attributes of a successful ‘I’ or infantry support tank, but it had two grave disadvantages. It was under gunned – it’s six -pounder gun with an AP range of 800 yards and nil HE performances 2 , had proved to be no match for the 75 and 88mm guns 3 of the ‘hull down’ or dug in German tanks they encountered during the advance up the Medjerda Valley.4"

1. So successful was the Churchill in Tunisia that the decison to stop further production was cancelled.
2. 6-pdr HE was extensively and successfully used by the North Irish Horse in the Oued Zarga mountains and the Battle for Longstop Hill. Also by 51st Bn. Royal Tank Regiment after receiving supplies of HE following its arrival in North Africa. 6-pdr A/P, which effectively took care of Tigers - a Churchill of the NIH was the first tank to knock one out - was much superior to that of the 75mm.
3. Churchills of the North Irish Horse, the 142nd and 145th RAC Battalions. No NIH tanks were lost and but three of the RAC were temporarily put out of action while clearing the enemy from the twin hills of Guerat el Atach. During this action 'C' Squadron NIH "captured six 88 mm. anti-tank guns, two of whose crews did not fire a shot." Source: NIH Battle Report.
4. The drive to Tunis was down the Medjerda valley not up.