What advantages would one get in reducing the maximum speed on a world war II line battleship to 15 knots? Longer range perhaps? Thicker armor? Less crewing and operating cost? Would overall construction cost be lower? What disadvantages would one get? It cant keep up with fleet carriers so it's no good as an escort. It can't dash to an area of operation quick enough. It will have to wage war at its own time and pace (!) Would its effectiveness as a fire support ship at land targets be impaired? Probably not. How about fighting in the line? Do battleships need to go at normal flank speed during a line battle? I read from somewhere that any speed higher than 20 knots makes accuracy past 10,000 meters very iffy. You could dash at 30+ knots only if you and your opponent are at a collision course (so your firing accuracy keeps improving as you approach each other at a certain combined speed.) In a rare one-on-one shootout with another BB, I reckon there's no serious disadvantage. High speed means you can position faster but that can be negated by other methods. You can outrun your opponent, but a battleship is supposed to stand and fight, not run away.