Although the unit saw no active service, it supplied trained gunners to siege batteries engaged on the Western Front during World War I.

[22] By October 1914, the campaign on the Western Front was bogging down into Trench warfare and there was an urgent need for batteries of Siege artillery to be sent to France.

The WO decided that the TF coastal gunners were well enough trained to take over many of the duties in the coastal defences, releasing Regular RGA gunners for service in the field, and 1st line RGA companies that had volunteered for overseas service had been authorised to increase their strength by 50 per cent.

Although the relevant WO Instruction does not specifically mention this, it is recorded that half the men of the new battery were Essex Territorials, and the remainder Durham miners (presumably Kitchener volunteers).

[27][28] Thereafter four more siege batteries ordered to be formed at Harwich had cadres of four officers and 78 other ranks (ORs) drawn from the Essex & Suffolk RGA:[29] 148, 220, 245 and 356 (see below).

A large number of other siege batteries were formed at Harwich during the war (34, 119, 139, 166, 189, 229, 252, 264, 294, 300, 312) and although no TF cadres are specified, it is likely that the Essex & Suffolk RGA would have assisted in their organisation.

[29] This process meant a continual drain on the manpower of the defended ports units and under Army Council Instruction 686 of April 1917, the coastal defence companies of the RGA (TF) were reorganised.

The Essex & Suffolk RGA serving in the Harwich and Shoeburyness Garrison was reduced from five remaining companies (1/1st, 1/4th, 2/1st, 2/3rd, 2/4th) to just three numbered 1–3.

[26] On 3 November 1915 the half battery from Harwich travelled to Roffey Camp, Horsham, to join the other personnel from Clarence Barracks, Portsmouth under the command of Maj W.H.

Clark had been the Regular Army adjutant of the Essex & Suffolk before the war and had applied to transfer to the battery from command of 67th Siege Bty.

[29][8][26][36][37][38] The battery joined 25th Heavy Artillery Group (HAG) with Fourth Army, which was preparing for that year's 'Big Push' (the Battle of the Somme).

On 13 November the battery swung its howitzers round to fire on Beaumont-Hamel (the Battle of the Ancre), the capture of which ended the offensive.

[43][45][46][47][48] There were minor operations on the Ancre Heights during January 1917, then in March the battery moved to the Arras sector where it supported Canadian Corps' successful attack on Vimy Ridge (9 April).

[38][51][52] At the end of June the battery was brought up to a strength of six howitzers when it was joined by a section (2 officers and 32 ORs) from 356th Siege Bty, which had also been formed with a cadre from the Essex & Suffolk RGA (see below).

[52][54] The Ypres offensive opened with the Battle of Pilckem Ridge) on 31 July, but after initial successes the attack bogged down before the end of the day.

[38][61][62][63] Early in 1918 62nd Bde moved south to join Third Army where its guns were hidden and remained silent until the launch of the German Spring Offensive on 21 March, when they immediately began firing pre-arranged 'SOS' barrages.

Afterwards, the battery took up a very exposed position at Pronville-en-Artois, near Quéant, and after being heavily shelled and suffering numerous casualties had to move into the valley behind.

It went out to the Western Front in August 1916, manning four 9.2-inch howitzers, and joined Fourth Army, which was engaged in the continuing Somme Offensive.

[29][38][37][69][70][71] The battery was commanded for a period by Major George Hugh-Jones, who had first been commissioned into the 1st Suffolk & Harwich RGA in 1900.

[8][72] In March 1917 148th Siege Bty moved north to join the artillery supporting Canadian Corps at Vimy Ridge, and then the continuing Arras offensive.

It went out to the Western Front 25 December 1916, equipped with four 6-inch 26 cwt howitzers, and initially joined 72nd HAG with Fifth Army on 7 January 1917 during the winter operations on the Ancre Heights.

[29][38][37][76] 72nd HAG followed the German withdrawal to the Hindenburg Line (Operation Alberich), and then joined Third Army for the opening Battle of Arras.

It returned to the line with Third Army and took part in the Hundred Days advance at the Battles of Albert, Bapaume and Cambrai, followed by the crossing of the Sambre.

[37][38] Its first major action was at the Battle of Messines, where it suffered numerous casualties under hostile CB fire, including its commander being wounded.

It then fired in support of the more successful battles of the Menin Road, Polygon Wood and Broodseinde, and suffered like the other batteries in the mud of Passchendaele.

[38][61][63][83] One of the most serious breakthroughs of the German offensive of 21 March 1918 occurred in front of 245th Siege Bty, and it was forced to pull out hurriedly with the loss of half its guns.

[83][85] 6th Brigade was with Second Army south of Ypres during the summer when 245th Siege Bty was hit by a German bombardment and its commander was killed.

[86][89] In 1938 the RA adopted the more conventional designation of 'regiment' instead of 'brigade' for a lieutenant-colonel's command, and the unit became the 'Suffolk Heavy Regiment on 1 November[87][86] On the outbreak of World War II the regiment was responsible for the following armament at Harwich:[90] With the danger of invasion after the British Expeditionary Force was evacuated from Dunkirk, a 'crash' programme began to instal additional guns at smaller ports, together with Emergency Beach Batteries at potential landing sites.

By March 1944 both district HQs had been disbanded and all the units came directly under HQ Coast Artillery, Eastern Command.

[116][119] The manpower requirements for the forthcoming Allied invasion of Normandy (Operation Overlord) led to further reductions in coast defences in April 1944.