Why the 1592 turtle ships must predate the invasion

The material demands of construction form the basis of the timing argument: seasoned timber, ironwork, oarsmen, sails, rigging, rope, and cannon could not have been gathered into a new warship in only a few weeks. The ship's rapid arrival therefore suggests that Yi Sun-sin and others had already studied older designs and prepared discreetly despite a court suspicious of conspicuous competence. Prewar preparation is evidence of Korean foresight and does not diminish the wartime achievement. The protected roof countered Japanese boarding tactics while openings allowed Korean artillery to remain effective, although the debated ironclad interpretation remains unresolved. Korean cannon could also fire darts and other ammunition rather than only solid shot, adding to the close-range danger the protected vessel could impose.