A Second World War minefield extending for 2.2 km along the coast between the eastern edge of St Mary's Marsh and Allhallows-on Sea. The minefield was seen as a strip closely delimited by a barbed wire fence on the landward side, and protected by a line of barbed wire on the seaward side. The actual minefield ranged from 15m to 30m in width and had traces of small craters (3-4m in diameter) at intervals where charges had been detonated, possibly at the time of removal. Larger craters from aerial bombing are also visible at points along the length of the minefield, but the lack of visible mine detonation coinciding with the bombing may indicate that the minefield had been lifted prior to the bombing raids. These defences were mapped from aerial photographs as part of the English Heritage: Hoo Peninsula Landscape Project.