Hill, Kenley and Chatham: in joint action with the fighters, the guns broke up the formations and shot down four aircraft, but the airfields at Biggin Hill and Kenley were badly hit. Next day a mass raid arrived over the Medway and flew up the Thames towards Hornchurch. They came under heavy fire from the 3.7s and 4.5s and 15 were shot down before the fighters took over. On 7 September heavy raids up the estuary attacked oil wharves at Thameshaven, Tilbury Docks and Woolwich Arsenal: a total of 25 aircraft were destroyed by AA guns and fighters. On 15 September, remembered as the zenith of the battle, the guns were in prolonged combat, especially with aircraft over Chatham in the morning, and again in the afternoon. The Blitz After 15 September the intensity of Luftwaffe day raids declined rapidly, and it began a prolonged night bombing campaign over London and industrial towns (The Blitz). This meant that the gunsites of 'Thames South' were in action night after night as the bomber streams approached the London Inner Artillery Zone (IAZ). This period of intense activity lasted until May 1941, but occasional raids kept the AA defences on high alert. On 12 July 1941 the experienced 206 (Erith) HAA Bty transferred to 60th (City of London) HAA Rgt. The regiment sent a cadre to 206th HAA Training Rgt, Arborfield, to provide the basis for a new 419 HAA Bty; this was formed on 10 April 1941 and joined the regiment on 7 July 1941 to replace 206 HAA Bty. The regiment later provided the cadre for 474 HAA Bty formed on 4 September 1941 at 207th HAA Training Rgt, Devizes, which joined 138th HAA Rgt. In the autumn of 1941 the regiment left 28 AA Bde and joined 5 AA Bde in 9th AA Division covering South West England, while 419 Bty joined 474 HAA Bty at 138th HAA Rgt in 9th AA Division on 17 December 1941. By May 1942 the regiment had transferred again, to 44th AA Bde in 4th AA Division in Manchester. However, that month the regiment left AA Command and prepared to go overseas as a mobile unit. In September 1942, 58th (Kent) HAA Rgt joined First Army with the following composition: 207 (Erith) HAA Bty 208 (Bromley) HAA Bty 264 (Dartford) HAA Bty 58 HAA Rgt Signal Section, Royal Corps of Signals 58 HAA Workshop