Why Japan lacked a centralized navy before the nineteenth century

Why did Japan not create a centralized navy before the nineteenth century?

Because daimyo needed transport more than centralized sea control and had political reasons to resist a national fleet; earlier wars did not create a strong tradition of battle-fleet operations.

The answer distinguishes using ships from maintaining a national navy. Maritime movement remained valuable, but daimyo treated ships mainly as transport and had political reasons to resist a centralized battle fleet that could shift power between domains. Japan's experience of the Mongol invasions emphasized shore fighting and the remembered divine wind rather than a durable institutional lesson in fleet warfare. This helps explain why an island society could remain deeply maritime without maintaining a national battle fleet.