During the first half of the 20th century, many cruise ships were signifiganly larger than battleships, why couldn't battleships be built as large?

by elicubs44
thefourthmaninaboat

The main reason for this was the available infrastructure, with dry docks being the most important example. Bringing a ship into a dry dock allowed for repairs and de-fouling to be carried out below the waterline. The size of the gates and dock put a strict maximum on the size of ship that could be accommodated, and they were expensive to expand. A liner would, generally, be travelling between major ports - any time it needed to be repaired, it would never be far from a large dock. The biggest liners, like the British Olympic or German Vaterland were built to run between New York and their home ports, with large dry docks at both ends of the voyage. Battleships, meanwhile, might have to operate far from their home ports, from foreign bases with much smaller dry docks than available at the home port. Liners could use foreign dry docks, but this was not a dependable option for a battleship (if a country relied upon another to be able to repair its battleships, what happens when they go to war?). Battleships were also much more likely to sustain damage, especially below the waterline.

IlluminatiRex

During that period it was a balancing act of a few primary factors: speed, guns, and armor. The amount of armor and guns directly impacted both the size and the weight of the vessel, and this in turn effected the speed.

At the time, the pinnacle of tactics during Naval Battles was what is known as "Crossing the T". Essentially, one line of ships would cut-off the other, and in doing so were able to bring all their guns to bear on their opponent. Likewise, their opponent could not bring all of their guns to bear to retaliate. This diagram shows what it would have generally looked like.

For a tactic like that to succeed you needed, as a battleship, a good combination of guns, speed, and armor. A classic example of this would be Admiral Count Heihachiro Togo and his victory over the Russians at Tsuhima in 1904. Both sides had guns that could fire at about the same range (and the bigger the gun, the bigger the range and the more destructive power). William Pakenham, who was a Royal Navy observer on-board Admiral Togo's ship, stated "when 12 inch guns are fired, shots from 10 inch guns pass unnoticed, while, for all the respect they instill, 8 inch or 6 inch might as well be pea shooters". Basically, the goal was to have the biggest guns possible on-board. This provides maximum firepower and range.

Admiral Togo had one more advantage over the Russians: Speed. He had about six or seven knots advantage over the Russians. If you have greater speed and range, then you can determine where and when the fight actually happens - by engaging the enemy from a longer distance and even moving away to keep that advantage. So if you can control those factors you can control the battle.

"Armor is speed" is something Jacky Fisher (important British admiral, key in the conception and design of HMS Dreadnought) is reported as having once said. This is because the more steel you put on the boat, the slower it is going to go. Unless of course you have new and more powerful methods of propulsion/power, which would allow you to attain a higher speed with more weight. Armor of course is important, as your ships need to be able to withstand hits. HMS Warsprite at Jutland for example, sustained 11 hits. While she was severely damage (and ordered home to Roysoth) she survived those hits and lived to see another day (a lot of days to be precise, she was engaged in WWII as well).

As u/Vonadler notes as well, money is a key issue. HMS Dreadnought cost approximately £1,784,000 in 1905. As an upgrade over other ship designs, she only cost £181,000 more. However, you have to multiply that by the amount of ships you want to build and then the number only gets more astronomical. In August 1914, the Royal Navy had 22 Battleships in commission (with 40 Pre-Dreadnoughts which are the older battleship designs that came before the Dreadnought in 1905) with another 13 under construction. And the price had only gone up since 1905. The Germans for example only had 15 built with 5 under construction. However I disagree that Vanguard was about 10 million GBP more to construct. Vanguard was built in the 1940s, 40 years after Dreadnought. Using [this inflation calculator] (http://inflation.stephenmorley.org/) I compared £11,530,503 in 1941 (the year that Vanguard was laid down) to 1905 (the year Dreadnought was laid down). In 1905, Vanguard would have cost about £5,291,677.27 pounds. A substantial increase to be sure, but only of about 297% compared to 546%. The overall point stands however, that bigger Battleships with more armor and whatnot do cost significantly more than their smaller counterparts.

And with ships you do not just have the cost of building. maintenance, crew (in the case of the German Battleships 1000+ crew members), fuel, etc... Those costs add up quickly. u/thefourthmaninaboat is also correct that the infrastructure was also a factor in Battleship design. On the other hand, cruise ships didn't really have to contend with all of this. They had their own design challenges to be sure, but armor for example wasn't really a factor.

This is my first "real" reply on this sub, so I hope it's been helpful and informative!

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