The "Kriegsmarine" (German navy) had at least three surface ships in the Loire estuary: a destroyer, an armed trawler and a Sperrbrecher (minesweeper), the last being the guard ship for the port. On the night of the raid there were also four harbour defence boats and ten ships from the 16th and 42nd Minesweeper flotillas berthed in the basin, while two tankers were berthed inside the Normandie dock. The 6th and 7th U-boat flotillas, commanded by "Kapitänleutnant" Georg-Wilhelm Schulz and "Korvettenkapitän" Herbert Sohler respectively, were permanently based in the port. It is not known how many submarines were present on the day of the raid. The submarine base had been inspected by the U-boat Commander in Chief, "Vizeadmiral" Karl Dönitz, the day before the raid. He asked what would they do if the base was subject to an attack by British Commandos. Sohler replied that "an attack on the base would be hazardous and highly improbable."