Defence batteries, Royal Artillery
The Defence Batteries were units of the Royal Artillery created for beach defence during World War II when the United Kingdom was threatened with invasion after the Dunkirk evacuation. Once they had served their purpose they were disbanded or converted into units of field artillery. Home defence. After the British Expeditionary Force was evacuated from Dunkirk and the UK was threatened with invasion, a crash programme of installing coastal artillery batteries was implemented in the summer of 1940. Later, as the Home Defence strategy developed, the Royal Artillery formed a number of 'Defence Batteries' to deploy  around the coastline for general beach defence. These were not part of the fixed defences of the RA's Coast Artillery branch covering the ports (although it had long been the practice for "garrison" artillery units to be equipped with a handful of mobile guns, in addition to their primary fixed guns, for similar usage), nor were they included in the field forces under Commander-in-Chief, Home Forces, but equipped with whatever old direct-fire guns were available they freed up scarce field artillery from semi-static beach defence for the mobile counter-attack forces. Most of these batteries  were formed on 1 September 1940. The batteries would have been formed around a cadre of gunners from existing units. For example, 901 (Independent) Defence Bty was commanded by an officer transferred from 135th (East Anglian) (Hertfordshire Yeomanry) Field Regiment, which was defending the Norfolk coastline with a variety of obsolete guns. The 135th also supplied 64 gunners, but these were recruits who had only just joined the regiment. Most of the defence batteries were grouped into regiments on 4 October 1940: Field Force. By the beginning of 1942 the imminent threat of invasion had passed, the coast artillery batteries  were fully established, and the RA required gunners for the field forces. The remaining defence regiments and independent batteries in the UK were disbanded or converted into field artillery on 12 January 1942: Most of these new field regiments served in reserve or holding formations, training reinforcements for units serving in active theatres, though 172nd Field Rgt did serve through the Tunisian and Italian campaigns, and 177th Field Rgt was used to reform the Regular Army's 25th Field Rgt, which had been captured at the Fall of Tobruk. Overseas. A number of defence batteries and regiments were also formed  during the war in British overseas garrisons: In addition, 965 Defence Bty, converted from 36 Heavy Bty, HKSRA, and equipped with 18-pdr and 2-pdr guns, served as part of the mobile coast defences of Hong Kong and was captured by the Japanese at the Fall of Hong Kong on 25 December 1941.