At major bases, guard-ship practice could scale into a squadron of eight, nine, or ten ships of the line. British formations usually relied on third rates because those vessels were numerous, whereas Dutch and other navies could make greater use of fourth rates; Britain often kept its fourth rates for distant peacetime stations. A vice-admiral of the port might command the force, with a rear-admiral and perhaps a commodore dividing it into subordinate groups. With roughly one-third crews, the ships could be made ready rapidly. Mobilising the entire formation created a direct trade-off because the port would lose the warships assigned to its own protection.
Notable Point · 8:23-9:49
How guard squadrons differed and what mobilising one cost
British ports usually relied on third rates while Dutch and other navies could use more fourth rates, but mobilising a whole guard squadron removed the port's own reserve protection.