During the Cold War the Royal Navy and US Navy operated SSBN forces out of Faslane and Holy Loch respectively. The UK identified that in any given period there were likely to be three distinct AGI patrols conducted around UK waters. It was noted that already AGI’s had been seen to deploy the Type 75 and 15 Sonobuoy in UK waters (intriguingly it is noted that the UK had recovered the Type 015 inside UK waters). Also of note was the scale of Soviet AGI efforts to track Submarine movements more generally. The buoys are normally modified on a Soviet AGI and deployed off a sensitive US naval base or submarine transit lane.