Plan Z:
German Carriers, Part Two

Even before the end of the First World War, several navies considered converting large ocean liners to full-decked aircraft carriers. Britain’s first aircraft carrier, Argus, had been laid down as the Italian liner Conte Rosso, while Germany drew up plans to convert the liner Ausonia.

After the Great War’s close, other nations studied liner conversions, but instead built their aircraft carriers as such from the keel up or converted battleships and battle cruisers made surplus by naval arms limitation treaties. Most navies drew plans for emergency conversions in case of war, and some like Japan even granted subsidies to steamship lines in exchange for building their liners to be easier to convert.

While the Allies built their new wartime fleet carriers as such from the start, all three Axis powers made serious attempts at converting ocean liners. The Japanese converted two into the fleet carriers Junyo and Hiyo, and others into escort carriers. The Italians got most of the way to completing the fleet carrier Aquila before leaving the Axis. And the Germans drew plans to rebuild the huge ocean liner Europa as an aircraft carrier.

Both the Japanese and Italians found that the conversions took far longer than estimated, even with the two Japanese ships having been built from the start for ease of conversion. The Japanese carriers were never the equal of purpose-built ships; Aquila never saw active service but also proved troublesome, though this was in part due to her age – thanks to the endemic corruption of the Fascist state, an older liner was selected for conversion rather than one of the larger, more modern ships that were available (but owned by influential shipping lines).

The ship chosen by the Germans gave them a great deal of trouble as well, at least at the design stage. Europa was an enormous ship, 936 feet long and displacing 56,000 tons (her sister Bremen was slightly larger); larger than most warships of the time but not as huge as the largest ocean liners (the Cunard Line’s famous “Queens” came in at over 80,000 tons apiece). Laid down at the height of the Great Depression, the technologically-advanced liners featured sealed high-pressure steam power plants complete with airlocks. These produced copious power, 135,000 horsepower, enough to comfortably exceed their designed speed of 27 knots. They also featured radical new hull forms with a bulbous bow (each ship sporting a slightly different design), reducing drag and smoothing their pitch in heavy seas.

Europa (left) and Bremen together at Bremerhaven, 1930.

Bremen and Europa both won the prestigious Blue Riband for the fastest average speed in an Atlantic crossing. With two such big and fast ships their owners, North German Lloyd, could maintain weekly service between New York and Europe where previous practice had required three ships. The two big liners also featured all the decadent amenities that the Roaring Twenties had to offer, plus a seaplane launched from a catapult when the ship neared port to speed the delivery of mail. When the Nazis came to power in 1933, Adolf Hitler ordered the abolition of class privilege on German ocean liners: passengers were now all equal and instead their cabins were designated by size and price.

When war came, Europa had completed a crossing and remained at Bremerhaven, while her sister was still docked in New York. Bremen slipped out of New York and eluded British patrols to reach the friendly Soviet port of Murmansk, then later made her way back to Germany (as seen in our Bismarck game).

The two great liners served as very large and well-appointed barracks ships, and the German Navy entertained schemes to use them as transports for the Operation Sea Lion, the invasion of Britain, and Operation Ikarus, the invasion of Iceland. Both were fitted to act as fast transports carrying a dozen tanks each, which would be landed from lighters.

Planning for a carrier conversion came later, in 1942, and initially involved only Europa. The naval architects had a number of problems with which to contend, similar to those which beset the Japanese and Italian projects. As a liner, Europa’s primary structural deck lay several decks higher than in a warship design. To accommodate a hangar, a box structure would have to be sunk into the structural deck, creating a myriad of problems. The Japanese had not faced this problem, as Junyo was designed to be converted; the Italians handled it by completely gutting the liner Roma when converting her into the carrier Aquila and only retaining the hull.

Europa as converted would have been unstable, with her center of gravity much too high; the Italians solved this problem with Aquila by adding large bulges under the waterline. The German design sketches don’t show bulges but they were discussed and doubtlessly would have been added eventually. Unlike the Italian ship, Europa would have retained her original boilers and turbines. She would have a powerful anti-aircraft armament, with a dozen 105mm guns and at least 56 light guns (with plenty of deck space to add more later).

German planning referred to Europa as an “auxiliary carrier,” sometimes translated as “escort carrier,” and called for an air group of 42 planes: 18 dive bombers and 24 fighters. She would have displaced over 49,000 tons as an aircraft carrier and had a designed speed of 26.5 knots. Such a massive ship would have been rather excessive for the typical escort carrier missions (chiefly, escorting).

Europa and her sister both appear in Second World War at Sea: Plan Z in carrier guise. Given the impractical nature of the planned German conversion – sinking the hangar into the structural deck appears to have been an exceedingly foolish notion, though to their credit her designers likely realized that the work would never actually be carried out - we’ve followed the “Italian solution” to give the ships a full conversion from the bottom up, retaining only the (bulged) hull like Aquila.

Compared to Aquila, Europa and Bremen would have been some 184 feet longer and 23 feet wider, and displaced over twice as much as the Italian flattop. Aquila would have operated 51 aircraft, so we’ve credited Europa and Bremen with 72 planes rather than the 42 of the initial design. That gives them the largest air group of any of the German carriers, but they are far from super-flattops. They have no armor, and their endurance is not what one might expect from a ship of that size – they consumed a great deal of fuel as liners and the designers predicted the same problem for them as aircraft carriers.

As with all the German carrier projects, service rivalry would have played a negative role. Not only would the ships need Luftwaffe cooperation to obtain planes and pilots for their own air group, ships of their great size would have been irresistible targets for Allied airmen. To remain operational, they would need a serious commitment of ground-based fighter cover over their bases and while leaving port.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and award-winning journalist, he has published over 100 books, games and articles on historical subjects. He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold.