How good was Italian battleship armour, and why did Italy prefer fast battleships to battlecruisers?
Short answerItalian protection was strong for its intended theatre, while a fast battleship could manoeuvre across the Mediterranean and still survive the close fleet action Italy expected against France.
NotesItaly cannot reach the open oceans without passing British-controlled chokepoints and exposing its coast to France. A commerce-warfare battlecruiser therefore offers less strategic value than it does to a global navy. Speed still matters because the Regia Marina must concentrate across the Mediterranean and choose favourable engagements. Caracciolo and the later Littorio lineage pair that mobility with the armour and heavy guns needed once avoidance gives way to battle.