More than two hundred requisitioned fishing vessels and roughly three to four hundred purpose-built trawlers gave the Royal Navy about six hundred of these small ships. The Isle class illustrates the common pattern: about twelve knots, 545 tons, and a crew of roughly forty. Although intended mainly for harbor security and defense, trawlers took on many other duties as wartime demand grew. A typical armament combined a 12-pounder or 4-inch gun, light anti-aircraft weapons, and depth charges. Crews often added whatever machine guns or other weapons they could obtain, leaving these auxiliary warships with highly improvised fits.
Chapter · 3:59-5:57
The Royal Navy's six-hundred-strong trawler fleet
The Isle class introduces a wartime force of roughly six hundred built or requisitioned trawlers used far beyond their intended harbor-defense role.