23 April 2018 marks the centenary of the British raid on the German held ports of Zeebrugge and Ostend on the Belgian coast. This daring assault was only partially successful in its attempt to block the ports and prevent their use by U-boats. It was marked nevertheless by extraordinary gallantry and Australian sailors were among those decorated for their courage.

But another, perhaps more significant operation was unfolding further north on the same day. The Imperial German Navy was under pressure. The U-Boat offensive was failing. Their losses remained low, but the average tonnage sunk had declined. The new convoy system was proving a significant challenge. The German army’s high command had lost faith in the U-Boats’ ability to win the war but, with its own ‘last throw’ offensive on the Western Front in progress, it appealed for a special effort against ships carrying Allied reinforcements.

This was easier said than done, but the High Sea Fleet’s commander, Admiral Reinhard Scheer, believed he could strike a heavy blow another way. Convoys to Scandinavia had already proved vulnerable to raiding German forces. The British had strengthened the escort but also enlarged the convoys, and thus their attractiveness as targets.

The plan was for battle cruisers under Admiral Franz von Hipper to lead an attack. If von Hipper were unable to brush aside the squadron of the Grand Fleet’s capital ships covering the convoy, he could call on the entire High Sea Fleet, which would follow him into the North Sea. This was a welcome change for Germany’s battle fleet, which had spent most of the previous 18 months in a defensive role, protecting the minesweepers that maintained the U-boats’ access to the open sea.

The raiding forces sailed early on 23 April 1918. The Germans had at last stopped using radio to pass preparatory messages and their communications security was excellent, helped by new call signs and a change in the cipher key on 21 April, which the British didn’t break for three days. Five British submarines were in the Heligoland Bight and one, J6, sighted the Germans. Unfortunately, its captain decided that the ships were forces covering a British minelaying operation and took no action.

The Germans’ own intelligence was poor. Their sortie coincided with a gap in the convoy schedule. Ironically, the covering force that returned to Rosyth on 24 April was one of the most vulnerable of any element of the Royal Navy’s Grand Fleet, the Second Battle Cruiser Squadron, comprising the four oldest of the type, led by HMAS Australia.

The German battle cruisers also had to do their own reconnaissance. Zeppelins were launched but recalled because of rising winds. This forced von Hipper to proceed nearly 60 degrees north, further than the High Sea Fleet had been since July 1914.

German progress was slowed by breakdowns and poor coal. Worse followed. The battle cruiser Moltke’s inner starboard propeller shaft snapped due to the failure of an old repair. The shaft and propeller broke off. The turbine shattered and debris penetrated pipes and machinery. Moltke rapidly took in 1,600 tons of water. Von Hipper was alarmed to receive the crippled ship’s signal at 0543 on 24 April that it was restricted to four knots. This breach of radio silence was justifiable with the ship at risk of being helpless in the open sea.

Moltke’s signal was picked up by the British. The text was not immediately decrypted, but the intelligence centre—‘Room 40’—identified the call sign. Unfortunately, the direction-finding fix on the transmission placed Moltke inland in Norway, causing doubts over its credibility. Finally, Room 40 decrypted a signal reporting German analysis that the British were unaware of German forces at sea. The inference was clear. The Admiralty ordered the Grand Fleet out at 1047. Despite the Firth of Forth being enveloped in thick fog, the entire fleet departed in less than three hours.

The High Sea Fleet didn’t linger. There was eventually no doubt that the intelligence was mistaken. After sighting the Norwegian coast, the German battle cruisers turned for home. The Moltke had been taken in tow while its engineers made repairs. By 1600, the battle cruiser’s portside shafts were turning. The Germans could be reasonably confident they had a clear run to the Heligoland Bight.

The geometry was probably obvious to the British. The Grand Fleet couldn’t get across the North Sea in time to intercept the Germans once the latter turned south. That they had done so was made clear by an Admiralty signal at 1625, which gave the position of the German flagship steering a course SSE. Room 40 decrypted a signal from U19 that reported ‘11 old enemy cruisers’ in a position that matched that of the High Sea Fleet.

J6 was not the only muddled submarine on patrol, although the U-Boats had the benefit of warning by ‘catchword’ signals that their fleet would be at sea—a clue Room 40 had missed. The Grand Fleet continued, but the High Sea Fleet was well ahead, helped by perfect weather that allowed Moltke to maintain speed until it cast off the tow at 1640. This was timely as the fleet was approaching the Bight, trammelled by minefields and submarines. The minesweeper M67 had already hit a mine and sunk.

J6 did no better a job on the High Sea Fleet’s return. After observing the German fleet, it surfaced and reported the sighting. However, giving priority to reporting was intended for outward contacts: J6 should have attacked. The British had a last chance with the submarine E42, fortunate to spot smoke in the late afternoon of 25 April. A dash south-east brought E42 in contact with Moltke’s formation. The submarine fired four torpedoes at a range of over 2,000 yards and was rewarded by a single explosion.

Moltke had spotted a torpedo and turned to avoid, but was hit abreast its port engine room at 1838. More than 1,700 tons of water flooded in, threatening Moltke’s ability to move. E42 was hunted, but remained unscathed. Hard work by the engineers meant that Moltke never lost steaming power and was safe at anchor next morning, but it wasn’t fully operational again until mid-September.

The Grand Fleet returned to harbour. The incident confirmed misgivings over the requirement to protect the convoys with a detachment of heavy ships, while the signals intelligence system could certainly have done better. Confirmation that Room 40 couldn’t be relied upon to provide warning every time heightened concerns, but perhaps the greatest failure lay in the poor assessments by J6’s captain.

The RAN battle cruiser Australia’s near-miss has been noted. Its loss defending a convoy in such circumstances might have had an interesting effect on Anglo–Australian relations, already scarred by Gallipoli.

A might-have-been more often suggested is that the US Navy formation, the Sixth Battle Squadron, had also covered earlier convoys. Destruction of the American force, when thus isolated from the Grand Fleet, would certainly have been a disaster for the Anglo–American relationship. Von Hipper’s battle cruisers, however, would have found the powerful American dreadnoughts a hard nut to crack, even if the German problems with coal and machinery didn’t negate their theoretical speed advantage.

Australia and its squadron mates certainly would have been fast enough to stay clear. Acutely aware of the risk of defeat in detail, the British or American admirals would have had to make unlikely errors to become entangled with the German main body. Scheer had already taken his fleet further away from its bases than it had been since July 1914. He would have had little appetite for a chase that risked a Grand Fleet getting between his ships and Germany.

The High Sea Fleet’s sortie was the last it would make before the armistice in November 1918. Poorly planned, the material problems showed just how seriously shortages of metals and skilled labour were affecting the fleet. Historians have long pondered why the German fleet did so little in the later years of the Great War. At least part of that inactivity may have been because it was becoming unfit to conduct sustained operations.

Between the blockade, finally fully effective once the United States had entered the war in 1917, the inefficiencies of the German federal system and the competing demands of other elements of Germany’s war machine, the High Sea Fleet was falling apart.