German U-Boat

Scapa Flow, which served as the main anchorage for the British Home Fleet during both World Wars is an open stretch of sea enclosed by the Orkney Islands, off the northern coast of Scotland. Stretching for ten miles at its widest, this natural harbor was flanked by the North Sea on the east and the Atlantic Ocean on the west. This strategic location held a key vantage point - for it enabled quick forays into either of these shipping routes.

Scapa Flow was viewed as an impregnable fortress, particularly against submarine attacks, not only because of the man made fortifications, but also due to the natural geographical aspects of the island. There were seven entrances, with the three main entrances protected by anti-submarine booms that could be opened to allow ships to pass. At the eastern end, lies another four channel entrances, but these were narrow and shallow with strong raging currents powerful enough, it was thought, to carry any U-boat off-course. In addition, the channels itself were subjected to high tides and low tides, bringing with it fluctuations from relatively fast currents to raging strong currents. The land around the channel was uninhabited.

During World War One, these four channel entrances were sealed off with blockships – rusty steel hulks filled with concrete that were sunk and held in place with heavy anchors. Moored mines and steel cables were installed as additional fortifications against any underwater penetration. Large search lights were strategically placed around the narrow entrances with the Flow itself patrolled by Royal Navy warships, searching for among other things, U-boats trying to slip through.

In the past, two attempts had already been made to breach the defenses of Scapa Flow. During the First World War, U-18 in 1914 and UB-116 in 1918 had attempted - both met with disastrous results. After the war, the base had not been used, and some of the fortifications were dismantled during peacetime. In 1938, however, when war with Germany seemed imminent, the defenses were again beefed up with additional sunken blockships added in the narrow channel entrance.

Any attack on the base would be fraught with danger and would require not only the highest level of seaman skills but also the nerves of steel and luck to pull it through. Any approaches had to be done from the surface, at night under the cover of darkness. The risks were high, not only because of the possibility of death or capture – that would be too easy, but even more at stake was the capture of an advanced German submarine beached in shallow coastal waters.

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