[3][4] The TA was doubled in size after the Munich Crisis and 56th A/T Rgt formed a duplicate regiment at Crosby, near Liverpool, on 9 May 1939.

Originally, this was to be 61st A/T Rgt, but the designation was changed to 66th Anti-Tank Regiment on 1 June, and it was recruited to full strength by July.

The 56th provided the defence on a section of the Dunkirk perimeter before being evacuated:[6] Following its return to the UK, the 56th lost men and batteries to form other units.

It became the first Royal Artillery unit to fly into battle – on board gliders – serving with 1st Airborne Division in Sicily in 1942 and later at Arnhem in September 1944.

This format was intended to help divisions distribute sub-units with balanced firepower and mutual support in close jungle fighting where battle groups often had to move independently.

161 Brigade joined XXXIII Corps, which was beginning to arrive at Dimapur, and fought in the Battle of Kohima while the remainder of the division reinforced IV Corps, whose land victory at Kohima and Imphal, in which the Division played an important part, proved to be the turning-point of the Burma Campaign.

[2][7] 66th Anti-Tank Regiment remained with 55th Division, serving in various parts of the UK, including a spell in Northern Ireland until July 1944, when it transferred to Home Forces.

[2] In December 1941, it sailed round the Cape in the same convoy as 56th A/T Rgt, and landed at Basra in Iraq on 1 February 1942, where it joined 8th Indian Division.

The regiment then served in North Africa, where it was commanded by Lieut-col Bill Leggatt, and Palestine until it was disbanded in December 1944.

In 1955, with the disbandment of Anti-Aircraft Command and the reduction in AA units, the regiment absorbed 293 (East Lancashire) LAA Rgt and 556 (East Lancashire) Heavy AA Rgt to form:[1][24][25] 380 Light Regiment (King's Own) Two years later, R Bty was redesignated R (King's Own) Bty.

During the regiment's time in England in 1940 to 1941, it underwent training on the new 6 Pounder Anti-Tank Gun, which was continued in India prior to its deployment with the 5th Indian Division.

While serving in Burma the regiment wore a white metal King's Own lion collar badge on a red/blue RA diamond patch on the turn-up of their bush hats.

After the war the regiment wore a red lanyard in place of the white RA one, which it retained as R Bty of 306th HAA Rgt.