The monument includes a World War II Heavy Anti-aircraft (HAA) gunsite, situated on the southern side of Lodge Lane, on the eastern outskirts of Cobham village, about 3km west of Rochester. The gunsite is located on the southern crest of a low ridge which forms part of the North Downs. The gunsite, known as TS15 (Thames South 15), formed part of a chain of anti-aircraft batteries, positioned to defend the industrial and military targets in the Thames and Medway Gun Defended Area from high flying enemy bombers approaching from the south and east. Sources indicate that the gunsite at Cobham was established by February 1940 and was armed with four 4.5 inch guns. The gun park occupied the south eastern corner of a polygonal, fenced enclosure which was entered by a gateway on Lodge Lane at its north western corner, or via the accommodation area to the north east. The perimeter fence has not survived, although a steel gatepost remains next to the former entrance on Lodge Lane. The gunsite consisted of a south east facing, semicircular arrangement of four octagonal gunpits, with a sunken magazine, located between the two forward emplacements, and a command post to the rear. Each emplacement contained a centrally placed gun, anchored to the concrete floor by a steel holdfast. The guns were surrounded by six roofed ammunition lockers protected by an outer, concrete blast wall, externally embanked with earth. The ammunition lockers survive, as do the external brick shelters for the gun crew, attached to each emplacement. The single storey, flat-roofed magazine is set within a sunken, concrete walled enclosure and is entered from the open passage to the rear, which also provides access to the smaller concrete structure situated opposite the magazine entrance. The internal dividing walls of the rectangular, five-bay magazine retain the painted grids on which the ammunition holding of each bay was recorded. The magazine passage is reached via a slope at each end, which leads down from the two forward gun positions. The roughly rectangular, concrete command post consists of three open bays at the front of the building, which held the fire control instruments, and a semi-sunken roofed element behind, which housed the plotting room and an adjacent rest room. The domestic camp was situated about 100m north east of the monument, and consisted of accommodation huts and associated structures flanking the entrance roadway from Lodge Lane. The camp buildings were reused for a short time after the war, as temporary shelters for the homeless, but were subsequently demolished, and this area is therefore not included in the scheduling. Only the ruined remains of the guardhouse survive on the southern side of Lodge Lane, although elements of hut foundations and connecting road surfaces may survive elsewhere within the camp area. All modern fixtures, fittings and materials associated with the stabling of horses within the magazine, and all modern fencing, are excluded from the scheduling, although the ground beneath these features, and/or the structures to which they are attached, are included. ASSESSMENT OF IMPORTANCE Although of comparatively recent date, 20th century military sites are increasingly seen as historic survivals representing a defining episode in the history of warfare and of the century in general; as such they merit careful record and, in some cases, preservation. One of the more significant developments in the evolution of warfare during this period was the emergence of strategic bombing in World War II, and this significance was reflected by the resources invested in defence, both in terms of personnel and the sites on which they served. During the war, the number of people in Anti-aircraft Command reached a peak of 274,900 men, additional to the women soldiers of the ATS who served on gunsites from summer 1941, and the Home Guard who manned many sites later in the war. A national survey of England's Anti-aircraft provision, based on archive sources, has produced a detailed record of how many sites there were, where they were and what they looked like. It is also now known from a survey of aerial photographs how many of these survive. Anti-aircraft gunsites divide into three main types: those for heavy guns (HAA), light guns (LAA) and batteries for firing primitive unguided rockets (so called ZAA sites). In addition to gunsites, decoy targets were employed to deceive enemy bombers, while fighter command played a complementary and significant role. Following the end of World War II, 192 HAA sites were selected for post-war use as the Nucleus Force, which was finally closed in 1955. The HAA sites contained big guns with the function of engaging high flying strategic bombers, hence their location around the south and east coasts, and close to large cities and industrial and military targets. Of all the gunsites, these were the most substantially built. There were three main types: those for static guns (mostly 4.5 and 3.7 inch); those for 3.7 inch mobile guns; and sites accommodating 5.25 inch weapons. These were all distinct in fabric, though they could all occupy the same position at different dates, or simultaneously by accretion. As well as the four or eight gun emplacements, with their holdfast mountings for the guns, components will generally include operational buildings such as a command post, radar structures including the radar platform, on-site magazines for storing reserve ammunition, gun stores and generating huts, usually one of the standard Nissenhut designs. Domestic sites were also a feature of HAA gunsites, with huts, ablutions blocks, offices, stores and amenities drawn from a common pool of approved structures. Sites were often also provided with structures for their close defence; pillboxes are the most common survivals, though earthwork emplacements were also present. The layout of HAA gunsites was distinctive, but changed over time, for example to accommodate the introduction of radar from December 1940, women soldiers from summer 1941, and eight gun layouts from late 1942. Nearly 1,000 gunsites were built during World War II, and less than 200 of these have some remains surviving. However, at only around 60 sites are these remains thought sufficient to provide an understanding of their original form and function. This includes 30 of the 192 examples which continued in use until 1955. Surviving examples are therefore sufficiently rare to suggest that all 60 well preserved examples are of national importance. Despite the loss of its domestic camp, the World War II Heavy Anti-aircraft gunsite (TS15), 250m east of Cobhambury Farm survives well and is one of only seven complete, or near complete, sites of its kind in Kent. The gunsite also provides the opportunity for typological comparison with similar batteries in the regional and national context, and represents an important physical record as well as a visual reminder, of the significant part played by ground based anti-aircraft guns in the defence of Britain during one of the most critical conflicts of the 20th century.