Song China and the Missing Sea-Going Warship

The Southern Song dynasty (1127-1279) possessed every component of naval power: magnetic compasses, gunpowder weapons, watertight bulkheads, multi-mast rigging, ships of 5,000 liao carrying 200-plus crew and merchants. It maintained a permanent standing navy of 20 squadrons and 52,000 men. Its merchant marine reached the Persian Gulf, Red Sea, and East Africa. Quanzhou was among the world's largest ports. And yet the Song never produced a sea-going warship. It never conducted an offensive coastal raid. It never landed troops behind enemy lines by sea. It never used its maritime resources to project military force across open water. This is not a marginal gap. It is a missing category. How does a polity with the world's most advanced ships, the world's largest navy, and direct access to Indian Ocean trade networks fail to produce even one vessel that can cross the open ocean and fight when it arrives?