The Dreadnought Battle Cruiser.
The following imaginary dialogue I composed in 1904 to illustrate the text that “Cruisers without high speed and protection are absolutely useless”:—
“The ‘Venus,’ an Armoured Cruiser, is approaching her own Fleet at full speed!
“Admiral signals to ‘Venus’: ‘What have you seen?’
“‘Venus’ replies: ‘Four funnels hull down.’
“Admiral: ‘Well, what was behind?’
“‘Venus’ replies: ‘Cannot say; she must have four knots more speed than I had, and would have caught me in three hours, so I had to close you at full speed.’
“Admiral’s logical reply: ‘You had better pay your ship off and turn over to something that is some good; you are simply a device for wasting 400 men!’”
The deduction is:
ARMOUR IS VISION.