A sudden 1939 capital-ship windfall would trigger a British building panic

How would the major navies react if several First World War capital ships and carrier conversions suddenly appeared in their fleets in 1939?

Japan, France, Germany, Italy, and the United States would all gain options, but four new Italian battleships would most immediately alarm Britain and accelerate British carrier and capital-ship construction.

Receiving hulls is different from turning them into usable combat power. France would need air groups for its new carriers, while Germany's damaged or dated ships would not all arrive at equal readiness. Japan and the United States would gain fast or aviation-capable ships. The sharpest British reaction would follow Italy's receipt of four additional Caracciolo-class battleships, which would remove any political case for pausing British carrier or capital-ship construction.