Scharnhorst and Gneisenau operated together for the early years of World War II, including sorties into the Atlantic to raid British merchant shipping.

Scharnhorst and several destroyers sortied from Norway to attack a convoy; the Germans were instead intercepted by British naval patrols.

During the battle of North Cape, a force led by the Royal Navy battleship HMS Duke of York sank Scharnhorst.

Debates in Germany over the role and size of its navy continued through the 1920s, when increased naval shipbuilding in France and the Soviet Union prompted the Germans to begin drawing up designs for large capital ships.

[11] In 1933, Adolf Hitler came to power in Germany; he made clear to the naval command that he had no intention of building a large fleet to challenge British supremacy at sea.

[13] He was also reminded that, despite the allowances of the Anglo-German Naval Agreement, the British had historically been sensitive about increases in main gun calibers aboard German capital ships.

[13] A plan to upgrade Gneisenau with 38 cm guns was proposed in 1942 while she was under repair, which also required lengthening the hull, strengthening the barbettes, and overhauling the electrical system, but this was abandoned in 1943.

[3] The German navy considered the ships to be poor sea boats; they were bow-heavy when fully equipped and very "wet" as high as the bridge.

This problem was mitigated to some extent by replacement of the straight stem with an "Atlantic bow" to both Gneisenau and Scharnhorst in January and August 1939 respectively; use of the "A" turret remained restricted in heavy seas.

They carried a number of smaller watercraft, including two picket boats, two launches, two barges, two pinnaces, two cutters, two yawls, and two dinghies.

Steam was provided to the turbines by 12 Wagner ultra-high-pressure oil-fired water-tube boilers, which produced pressures up to 58 standard atmospheres (5,900 kPa) and temperatures up to 450 °C (842 °F).

[3] The Scharnhorst-class ships were built with a main battery of nine 28.3 cm (11.1 inch) SK C/34 54.5 caliber quick-firing guns in three triple turrets, two forward and one aft.

[19] Muzzle velocity for the AP shells was 890 meters per second (2,920 feet per second); the guns were expected to fire 300 rounds before enough wear had been incurred to warrant replacement.

Also, the beam of 30 m meant that the protection system had to be weaker around the main battery turrets, as a significant amount of the hull space was taken up by the magazines and barbettes.

[35] On 7 April 1940, Scharnhorst and Gneisenau formed the primary covering force for the invasions of Narvik and Trondheim in Norway during Operation Weserübung.

At 04:30 on 9 April, the Seetakt radar on Gneisenau picked up a contact, beginning the action off Lofoten; both ships went to battle stations.

Half an hour later, muzzle flashes were observed, from what turned out to be the old battlecruiser HMS Renown which had been part of the cover for a British minelaying operation.

After operations in the Arctic Sea that resulted in the sinking of several British ships, Admiral Hipper and the destroyers were detached to refuel in occupied Norway.

At 16:45 on 8 June, Scharnhorst and Gneisenau spotted the British aircraft carrier HMS Glorious, which was escorted by the destroyers Acasta and Ardent, at a range of around 50,000 m (55,000 yd).

Before she sank, Acasta launched four torpedoes at Scharnhorst; the ship evaded three, but the fourth struck the starboard side near the rear gun turret.

[41] The torpedo hit caused significant damage to Scharnhorst; several watertight compartments, including parts of the starboard engine room, were flooded, she took on a list of 3°, and she was 3 m (9 ft 10 in) down by the stern.

[43] Under the command of Admiral Günther Lütjens, Scharnhorst and Gneisenau broke into the Atlantic in late January 1941 to raid convoys between North America and Great Britain.

Scharnhorst had suffered repeated problems with defective superheater tubes in her boilers and this needed the repair facilities that existed in the French naval dockyard.

[54] The two 454 kg bombs penetrated both armored decks, all the way down through the double bottom, before coming to rest on the sea floor; they failed to explode.

[55][56] In early 1942, the crews of Scharnhorst, Gneisenau, and the heavy cruiser Prinz Eugen made preparations for Operation Cerberus, a daylight dash up the English Channel.

At 15:31, Scharnhorst detonated a magnetic mine, which damaged the ship's circuit breakers enough to shut down the entire electrical system.

At 16:17, five British destroyers attempted to torpedo the German ships, but heavy fire from Gneisenau and Prinz Eugen mauled one and forced the others to turn away.

Attempts to sail on 7 and 23 January were aborted after the navy received reports of heavy activity at British air bases in Britain.

For 6 months, fuel shortages curtailed any major operations by Scharnhorst or the other ships in Norway,[64] which included the battleship Tirpitz and the heavy cruiser Lützow.

Admiral Bruce Fraser, aboard the battleship HMS Duke of York, was some 270 miles away, and steaming to cut off Scharnhorst after she was engaged by the three cruisers.