Why Bordeaux's blockade runners mattered

The plan called for Royal Marines to leave a submarine in folding kayaks, paddle up the Gironde, attack shipping at Bordeaux, and then escape overland toward Spain. Bordeaux sat deep in the Bay of Biscay, away from convenient bomber routes and awkwardly placed for British naval patrol axes. German blockade runners could cross the exposed approaches at speed and then slow in safer coastal waters, while bombing alone had not made the harbor unusable. A small kayak force therefore offered a way to disrupt critical overseas supplies to Germany where conventional attack had limited leverage.