21st Army Tank Brigade The 21st Army Tank Brigade was a British Army formation active during World War II . It served with the British First Army and the British Eighth Army during the battles in Tunisia and Italy . History . In 1939 it was a First Line Territorial Army Brigade stationed in the United Kingdom . It was assigned to Eastern Command defending the south - eastern portion of the country . Equipment shortages prevented it from receiving any significant numbers of modern tanks , obsolete Vickers Medium Mark II and Mk II Light Tanks comprising most of the armour on hand until after the Battle of Dunkirk . Shortly after that battle the brigade HQ was pulled back to the Salisbury Plain although each tank battalion was detailed as a mobile reserve for the infantry divisions holding the coastline . Each regiment could only form a single mobile squadron , the remaining two serving as infantry . In August 1940 it began to receive modern Valentine I tanks , the first of what would be a continual change in tanks . Valentine IIs were received from April 1941 and the brigade had about a hundred Churchill tank s on strength by the end of the year . The brigade lost 44th Royal Tank Regiment on 11 September 1940 , but 43rd Royal Tank Regiment wasn ' t assigned until 9 November 1940 . 42nd Royal Tank Regiment was transferred away on 12 April 1941 and 43rd Royal Tank Regiment was exchanged for 12th Royal Tank Regiment on 12 April 1941 . 145th Regiment Royal Armoured Corps arrived on 15 November 1941 . This left the brigade with 12th and 48th Royal Tank Regiment and the 145th Royal Armoured Corps , the units which it would keep for the bulk of the war . The brigade was redesignated as the 21st Tank Brigade on 6 June 1942 when it was assigned to the 4th Infantry Division as part of the British experiment with " Mixed Divisions " . A mixed division had one tank brigade with infantry tank s and two non - motorized infantry brigades ; the idea being to better coordinate tank and infantry support . The 4th Division , with the brigade , didn ' t arrive in North Africa until the end of March 1943 , although it helped to break open the approaches to Tunis in April . The battle was extremely costly , 48th RTR alone losing 38 Churchills during the fighting , and the mixed division was judged a failure for lack of infantry to fight through difficult country . The division remained behind in North Africa until another infantry brigade could be assembled to replace the 21st Tank Brigade . The brigade was finally relieved of its assignment on 12 December 1943 by the 28th Infantry Brigade , but wasn ' t transferred to Italy until May 1944 . In the meantime it was reorganized and reequipped with new Churchill V close - support tanks and Stuart light tanks replaced the Bren Carrier s in its reconnaissance troops . Most of these had their turrets removed . Many of its Churchills had their 6 pdr guns bored out to accept American ammunition or simply replaced by guns and their mounts from damaged Sherman tanks ; these were known as Churchill NA75 ' s . A number of Shermans were put into service by the regiments of the brigade . This gave each regiment a wide variety of tanks in service . For example in September 1944 12th RTR had 6 Churchill I ' s , 6 Churchill V ' s , 23 Churchill III / IV ' s with the 6 pdr gun , 6 Churchill NA75s and 12 Shermans . It remained under the direct command of the Eighth Army after it arrived in Italy until it was subordinated to the I Canadian Corps on 7 July 1944 , but saw no action until it supported the Canadian attack on the Gothic Line on 31 August 1944 . In December 48th RTR was temporarily detached to support the 43rd Gurkha Infantry Brigade while 145th RAC was disbanded and replaced by the North Irish Horse . In January 1945 it began to receive " heavy " Churchill VIIs and converted to an all - Churchill structure . In February it came under the command of the V Corps and supported its various units during Operation Grapeshot , the Allied offensive in the Po Valley . On 11 June 1945 it reorganized as the 21st Armoured Brigade .