[2][3][4][5][6] When the Territorial Force (TF) was created by the Haldane Reforms in 1908, a new unit was formed at Chelmsford under the title Essex (Fortress) Royal Engineers.

[11][12] As well as operating searchlights for the coastal defence guns, the RE fortress companies began to use them in the Anti-Aircraft (AA) role as the war progressed and raids by airships and fixed wing bombers on the East Coast became more frequent.

[13] As a naval base, Harwich was a tempting target and, although the town was darkened, German aircrews could still recognise it from harbour lights and the outline of the power station and railway.

It was attached to 54th (East Anglian) Division (TF) in peacetime, but its wartime role remained as part of the Harwich defences.

Its place in the Harwich coast defences was taken in 1936 by a newly formed unit, the Suffolk (Fortress) RE (TA), which raised an Electric Lights and Works Company at Ipswich.

[25] In May, the first, very secret, Searchlight Control (SLC) radar sets began to appear, with one being stationed at Landguard Fort to replace the old sound-locator at the S/L site operated by 469 AA Co.[25][28] The Phoney War ended with the German invasion of France and the Low Countries on 10 May 1940.

A plan to attach groups of riflemen from the infantry training centres to 6 AA Division's widely spaced S/L sites foundered on the lack of men.

Instead, the S/L detachments themselves were given the responsibility for attacking parachutists before they could organise, and spare men at company HQs were formed into mobile columns using requisitioned civilian transport to hunt them down.

[19][21][22][29][30][31] During the Battle of Britain, the subsequent London Blitz, on into 1941, the regiment remained part of 29 AA Bde covering Harwich and East Anglia.

The cluster system was an attempt to improve the chances of picking up enemy bombers and keeping them illuminated for engagement by AA guns or RAF Night fighters.

[36] The regiment supplied a cadre of experienced officers and men to 236th S/L Training Rgt at Oswestry where it provided the basis for a new 559 S/L Bty formed on 13 February 1941.

[38][39][40] Early in 1942, the Luftwaffe began a new wave of attacks on British cities (the Baedeker Blitz):in 8 AA Division's area Exeter and undefended Bath were hit in March, April and May, and Weston-super-Mare in June.

[41][44][45][46] By the end of 1944, 21st Army Group fighting in North West Europe was suffering a severe manpower shortage, particularly among the infantry.

[47] At the same time, the German Luftwaffe was suffering from such shortages of pilots, aircraft and fuel that serious aerial attacks on the United Kingdom could be discounted.

[19][22][29][31][30][49] It was redesignated again on 12 February 1945 as 613rd (Essex Fortress) Infantry Regiment, RA and joined 21st Army Group on line of communication duties in April 1945.

This, however, was not a descendant of the original 855, but was raised at Salford near Manchester by amalgamating existing independent AA Reporting Troops in the area.