How did the Tang people gain the Mandate of Heaven? Song rulers grew weak and quarreled among themselves.
Arab traders took over the Silk Road trade, which undermined the Tang economy.
Tang invaders from the far north overthrew the Sui dynasty.
A Sui official led a rebellion that caused the Sui dynasty to collapse

What was the national government’s biggest concern if facing a war, under the articles of confederation? the national government had no national military. the country had grown too large to defend with a small army. the states would not back the federal government. there was no way the states would pay for fighting a war.