73rd Heavy Anti-Aircraft Regiment, Royal Artillery

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.[8] In February 1939 the existing AA defences came under the control of a new Anti-Aircraft Command. In June a partial mobilisation of TA units was begun in a process known as 'couverture', whereby each AA unit did a month's tour of duty in rotation to man selected AA and searchlight positions. On 24 August, ahead of the declaration of war, AA Command was fully mobilised at its war stations.[9]

On the outbreak of war, 73rd AA Rgt under the command of Lieutenant-Colonel A.L. Wood, MC, TD, formed part of 34th (South Midland) Anti-Aircraft Brigade based at Coventry in 4 AA Division,[4][7][10] but in November 1939 it deployed to France with the British Expeditionary Force.[11][12]

When the Battle of France began in May 1940, 73rd HAA Rgt was part of 12 AA Bde defending the airfields of the RAF Advanced Air Striking Force (AASF) with semi-mobile 3-inch guns of 1918 pattern.[13][14][15][16] The regiment was deployed to defend some of the southern airfields: Lt-Col Wood with RHQ was at Chouilly, east of Épernay, 209 AA Bty with eight guns was at Écury and Athis, 311 AA Bty's eight guns were distributed to Matougues, Saint-Mard-lès-Rouffy and Le Mesnil-sur-Oger, while 210 AA Bty was detached to 2 AA Bde covering airfields north of the River Somme (see below). The first GL Mk. I gunlaying radar sets had arrived amidst much secrecy.[17]

The AASF airfields came under attack at the start of the campaign, subjected to dive-bombing and low-level attacks with which the old 3-inch guns and their Vickers Predictor No 1 and height-finders could not cope. Soon the AASF had to send depleted squadrons back to the UK, and reorganise as a mobile force to withdraw in front of the advancing Germans, while its bombers continued to attack enemy communications.[17][18][19][20][21]

The German Blitzkrieg attack soon cut off the bulk of the BEF's fighting formations and forced them to withdraw to Dunkirk for evacuation to England. However, even after the Dunkirk evacuation ended at the beginning of June, the AASF, a number of fighting formations and a large number of rear echelon units were still in France south of the Somme, and fresh British forces were being landed at Cherbourg. 12 AA Brigade set off to join this new concentration, its regiments 'trundling their old 3-inch guns at their maximum speed of 10 to 12 mph, though Vendôme, Le Mans and Rennes on the long haul westwards'.[22][23][24]

However, the situation in France was beyond remedy, and the British government decided to evacuate its remaining troops from the Atlantic ports between 15 and 17 June (Operation Ariel). Detachments of 73rd HAA Rgt maintained temporary cover for 72 hours along the route of the evacuation, and two of its precious GL radar sets were got away from Saint-Nazaire by 79th (Hertfordshire Yeomanry) HAA Rgt, but the rest of the equipment had to be destroyed on the dockside. Personnel embarked under attack by the Luftwaffe and the RMS Lancastria, with some parties of 73rd HAA Rgt aboard, was sunk off Saint-Nazaire with heavy loss of life.[22][25][26][27]

In April 1940, 210 AA Bty was detached to 2 AA Bde, which was responsible for defending the airfields of the BEF's Air Component north of the Somme. The battery deployed six 3-inch guns at Mons-en-Chaussee and two at Peronne Civil Airport under the command of 60th (City of London) AA Rgt. However, 210 Bty only had two gun tractors for these semi-mobile guns. Each airfield was also defended by a Troop from 8 Bty of 2nd Searchlight Rgt.[28]

Once the Germans had broken through, 210 Bty was ordered to reposition on 16–17 May, with Bty HQ (BHQ), a four-gun Trp and a S/L Trp at Conteville airfield, and the other gun and S/L Trps at Crécy airfield. They were in position on 18 May the day that Peronne fell to the Germans.[28]

By now, the RAF's fighter squadrons were withdrawing from France and on 20 May 210 Bty, accompanied by the two Trps of 8 S/L Bty, was ordered to withdraw from Conteville and Crecy. 2nd S/L Regiment lent towing vehicles to get the guns away. Initially they were ordered to Saint-Pol, then to Saint-Omer and finally to move south-west to Rouen to come under 3 AA Bde. However, 2nd Panzer Division was already in Abbeville blocking the way, and the battery had to fight a rearguard action with enemy ground troops to get to the coast at Boulogne. Although it had to abandon its guns, they had been disabled and the battery had got away with all the instruments and breechblocks. One officer and eight other ranks had been lost in the rearguard action. The battery left Boulogne before it came under attack and made it back to Dunkirk, where the BEF was preparing its evacuation (Operation Dynamo). On 26 May 210 Bty was ordered back to the UK to reform.[28][29]

3.7-inch HAA gun preserved at Imperial War Museum Duxford.

AA units evacuated from France were rapidly reinforced, re-equipped where possible, and redeployed for future integration into existing defence plans. 73rd AA Regiment, with 209, 210 and 311 Btys under command, went to No 1 AA Practice Camp, Aberporth, where it re-equipped with 3.7-inch guns.[30] On 1 June, those AA regiments equipped with 3-inch or the newer 3.7-inch were termed Heavy Anti-Aircraft (HAA) to distinguish them from the new Light Anti-Aircraft (LAA) units being formed.[2][5]

After re-equipping, the regiment was posted to 43 AA Bde in 7 AA Division tasked with guarding Middlesbrough during the Blitz.[12][31][32][33]

In late May 1941, the regiment transferred to 42 AA Bde defending Clydeside in 12 AA Division, and then left AA Command entirely during the summer to join the War Office Reserve to train for overseas service.[34][35]

The regiment arrived in Egypt with 209, 210 and 311 HAA Btys early in 1942 and served in Middle East Forces.[12][27][36] It remained defending base areas in Egypt throughout the North African Campaign. In early 1943 its 24 3.7-inch guns were deployed under 18 AA Bde in Eighth Army defending Alexandria, Aboukir, Matruh and the landing grounds of the Desert Air Force.[37]

The regiment concentrated at Suez in June 1943 to prepare for the Allied invasion of Sicily (Operation Husky).[27] For this operation, eight composite beach groups were formed to defend the landing points as soon as possible after Zero Hour, each of which included an HAA Bty organised on a light scale for assault landing. The availability of Landing Ships, Tank (LSTs) made it feasible to land suitably waterproofed 3.7-inch guns and GL radar sets in the first wave of the attack. The HAA Troops were equipped with a new GL radar system, the No 3 Mark III, or 'Baby Maggie', which had its transmitter, receiver, aerial array and operating display all carried in a two-wheeled trailer towed by a 3-ton truck. 209 and 311 HAA Batteries were each assigned to one of these beach groups and sailed from Egypt to take part in the landings.[38][39][40]

The assault landings began at 02.45 on 10 July 1943. The advance parties of the AA units attached to the beach groups landed from Landing Craft Infantry (LCIs) as infantry prepared for a firefight, but there was only light opposition and they were soon able to move to the sites selected for gun positions when the LSTs arrived about 4 hours later, although the 'Baby Maggies' had failed to stand up to the rough handling of the landings. More importantly, radio communications with the AA HQ ship broke down for the first 48 hours after landing, and defensive fire was reduced to crude 'barrage' methods. The rest of 73rd HAA Rgt arrived at Syracuse on 13 July with the Tactical HQ of 2 AA Bde. After the landings, Eighth Army made rapid progress up the east coast of Sicily and the follow-up AA forces began to land. 62 AA Bde HQ arrived in Syracuse on 17 July, taking over responsibility for the port's defence.[27][40][41]

While the Eighth Army invaded mainland Italy in September (Operation Baytown), 73rd HAA Rgt remained at Syracuse waiting to join it.[27][41] It appears to have crossed to the mainland briefly, but by January 1944 it was back in Sicily guarding Augusta under 73 AA Bde.[27][42] It finally moved to Italy, leaving Augusta on 7 October arriving at San Stefano on 20 October, and joining 66 AA Bde.[27][43]

3.7-inch HAA gun in action in the field artillery role in Italy.

66 AA Brigade was providing AA defence for Leghorn (Livorno), which was Fifth US Army's main supply base. However, there was little Luftwaffe activity apart from occasional high-level reconnaissance aircraft flying over the port. By January 1945, the regiment had rejoined 62 AA Bde, which was close up to Fifth Army's positions facing the Gothic Line. With little call for AA defence, 62 AA Bde employed its versatile long-range 3.7-inch guns in a medium artillery role against ground targets. This included counter-battery (CB), defensive fire (DF) and harassing fire (HF) shoots, but also air-burst shoots against entrenched positions, and destruction of hard targets such as buildings.[43][44]

By now, the Allied forces in Italy were suffering an acute manpower shortage, and surplus AA units were being disbanded in increasing numbers. On 14 January 1945, the regiment was told that it was to be placed in suspended animation. Most of the personnel were reassigned by mid-February and the process was completed by 31 March.[2][5][4][12][27][43][45][46]