Gunter Priens log continues from 13th October, as he moves into the Royal Navy anchorage at Scapa Flow
0027 It is disgustingly light. The whole bay is lit up. To the south of Cava there is nothing. I go farther in. To port, I recognize the Hoxa Sound coastguard, to which in the next few minutes the boat must present itself as a target. In that event all would be lost; at present south of Cava there is no shipping; so before staking everything on success, all possible precautions must be taken.
0055 Therefore, turn to port is made. We proceed north by the coast. Two battleships are lying there at anchor, and further inshore, destroyers. Cruisers not visible, therefore attack on the big fellows. Distance apart, 3000 meters.
0116 (time queried in pencil, 0058 suggested) Estimated depth, 7.5 meters. Impact firing. One torpedo fixed on the northern ship, two on the southern. After a good 3 1/2 minutes, a torpedo detonates on the northern ship; of the other two nothing is to be seen.
0121 (queried to 0102) (suggested time 0123, in pencil) About! Torpedo fired from stern; in the bow two tubes are loaded; three torpedoes from the bow. After three tense minutes comes the detonation on the nearer ship. There is a loud explosion, roar, and rumbling. Then come columns of water, followed by columns of fire, and splinters fly through the air.
The harbor springs to life. Destroyers are lit up, signaling starts on every side, and on land 200 meters away from me cars roar along the roads. A battleship has been sunk, a second damaged, and the other three torpedoes have gone to blazes. All the tubes are empty. I decide to withdraw, because: (1) With my periscopes I cannot conduct night attacks while submerged. (See experience on entering.) (2) On a bright night I cannot maneuver unobserved in a calm sea. (3) I must assume that I was observed by the driver of a car which stopped opposite us, turned around, and drove off towards Scapa at top speed. (4) Nor can I go further north, for there, well hidden from my sight, lie the destroyers which were previously dimly distinguishable.
0128 At high speed both engines we withdraw. Everything is simple until we reach Skildaenoy Point. Then we have more trouble. It is now low tide, the current is against us. Engines at slow and dead slow, I attempt to get away. I must leave by the south through the narrows, because of the depth of the water. Things are again difficult. Course, 058, slow – 10 knots. I make no progress.
At high speed I pass the southern blockship with nothing to spare. The helmsman does magnificently. High speed ahead both, finally 3/4 speed and full ahead all out. Free of the blockships – ahead a mole! Hard over and again about, and at 0215 we are once more outside. A pity that only one was destroyed. The torpedo misses I explain due to faults of course, speed, and drift. In tube 4, a misfire.
The crew behaved splendidly throughout the operation. On the morning of 13/10, the lubricating oil was found to have 7-8% water in it. All hands worked feverishly to change the oil, i.e. to get rid of the water and to isolate the leaking point. The torpedo crews loaded their tubes with remarkable speed. The boat was in such good form that I was able to switch on to charge in the harbor and pump up air.
0215 Set SE course for base. I still have 5 torpedoes for possible attacks on merchantmen.
A full account, including charts is at U-47.org .