Fort Lytton was Brisbane's primary defence facility from the colonial era until after WW2. In the late 1880s and 1890s Fort Lytton was very advanced technologically, with an electrically operated minefield across the Brisbane River, an electrically-operated search light, its own electricity generating station, and supporting high-tech garrison artillery including disappearing guns with projectiles that could penetrate up to 12 inches (30cm) of steel plate. Fort Lytton also had infantry and field artillery defensive support. Fort Lytton remained the centre of military activity in Queensland well into the 20th century. In WW2 Fort Lytton was critical to the defence of the submarine base in the Brisbane River that was home to over 80 US submarines. The defences included electronic detection of both surface vessels and submerged submarines, a boom net and gate across the river, ship boarding and inspection teams, supporting garrison artillery, a radar station, a signal station and a heavy anti-aircraft battery.