What was the point of a semi-dreadnought battleship?
Short answerIt was a transitional modernization of the pre-dreadnought pattern built while the all-big-gun design was still being understood.
NotesSemi-dreadnoughts were not created to fill a coherent permanent category. They appeared while Dreadnought-type ships were entering service but established pre-dreadnought programs were still moving through design and construction. Navies enlarged the secondary heavy battery and updated the older pattern as far as practical. The result was a transitional ship produced by institutional timing rather than a settled doctrine.