The brigade, now known as the 'Black Rats', was formed in 1939 and fought in the Second World War in the Western Desert Campaign in North Africa. The Black Rats were subsequently involved in the invasion of Sicily and fighting in Italy before taking part in the Battle of Normandy and the advance through Belgium, Holland and into Germany. A Roll of Brigade, commanders and an order of battle complete this useful history, that was originally published in July 1945, shortly after the surrender of Germany.

In September 1939, at the start of the Second World War, this brigade changed its title from Heavy Armoured Brigade (Egypt) to 4th Armoured Brigade. On 27 July 1941, it handed over its units to the 1st Army Tank Brigade and received new units based in Egypt. It was reformed again when the HQ arrived in Sicily and it took control of new units there. The 4th Armoured Brigade saw service in the North African Campaign, the Allied invasion of Sicily, the Italian Campaign and in North-western Europe. Although it served under many different formations, it was most famous as part of the 7th Armoured Division, the 'Desert Rats'.

The 4th Armoured Brigade left the 7th Armoured Division in North Africa in 1943, to return to join the Allied invasion force for Normandy. In June 1944, the brigade landed in Normandy as an independent brigade and fought in the Battle of Normandy during the battle for Caen. Notably, the 4th Armoured Brigade was the first to cross the Rhine into Germany.