(RA). In these postwar years, the medium artillery was still equipped with wartime 60-pounders and 6-inch howitzers. On 1 October 1932, 219 (Durham) Med Bty transferred to the 54th (Durham & West Riding) Medium Brigade and was replaced in 55th Med Brigade by 152 Heavy Bty from Tynemouth Heavy Brigade, which converted to medium artillery. In the 1930s, the increasing need for anti-aircraft (AA) defence for Britain's cities was addressed by converting a number of TA units to that role. The 55th (Northumbrian) Medium Brigade became the 63rd (Northumbrian) AA Brigade on 10 December 1936, and reorganised as three batteries (152 Medium Bty transferred to 64th (Northumbrian) AA Brigade). The unit formed part of the 30th (Northumbrian) AA Group in the 2 AA Division. 63rd (Northumbrian) Anti-Aircraft Brigade, RA HQ at Drill Hall, The Green, Sunderland 176th (County of Durham) Anti-Aircraft Bty at Drill Hall, The Green, Sunderland 177th (County of Durham) Anti-Aircraft Bty at Drill Hall, Seaham Harbour 178th (County of Durham) Anti-Aircraft Bty at Drill Hall, The Green, Sunderland On 1 February 1938 an additional battery, 220 AA Bty, was formed for 63rd AA Brigade by conversion of 186 and 216 Medium Btys from 54th Medium Brigade. However, it was transferred to a new 85th (Tees) AA Brigade forming at Middlesbrough as part of the expansion of the TA following the Munich Crisis. It was replaced in 63rd AA Brigade on 1 November 1938 by another new battery, 269 AA Bty at Seaham Harbour, formed by conversion of B Company, 6th Battalion, Durham Light Infantry. On 1 January 1939 the RA replaced its traditional unit designation 'Brigade' by the modern 'Regiment', which allowed the 'AA Groups' to take the more usual formation title of 'Brigades'. World War II Mobilisation and Phoney War The TA's AA units were mobilised on 23 September 1938 during the Munich Crisis, with units manning their emergency positions within 24 hours, even though many did not yet have their full complement of men or equipment. The emergency lasted three weeks, and they were stood down on 13 October. As international tensions increased, the TA's AA strength grew rapidly, all the AA defences came under the control of a new Anti-Aircraft Command in February 1939. In June 1939. a partial mobilisation of the TA was begun in a process known as 'couverture', whereby each AA unit did a month's tour of duty in rotation to