The entire force , now including the yielding commander , sailed down the Yangtze .
The forts along the way fell , as this commander , now allied with the Mongols , had also commanded many of the down - river garrisons .
The entire force , now including the yielding commander , sailed down the Yangtze , and the forts along the way fell , as this commander , now allied with the Mongols , had also commanded many of the down - river garrisons .