The Royal Navy's Porpoise-class minelayers reflected the continuing importance of submarine-laid mines in the 1930s. On the First World War figures cited here, minelaying appears to be one of the most effective forms of submarine warfare. The attacking boat accepts relatively little immediate risk because it departs before the minefield begins damaging traffic. A cruiser submarine with this capability can threaten one area with mines while operating somewhere else with guns and torpedoes.
Notable Point · 29:23-30:00
Minelaying gives cruiser submarines influence without lingering
First World War experience makes minelaying an attractive secondary role because a submarine can create enduring danger and leave before its weapons strike.