However , it was unable to defeat incursions by the Later Zhou between 956 and 958 , and ceded all of its land north of the Yangtze River .
With this , Southern Tang became the undisputedly most powerful regime in southern China .
It was unable to defeat incursions by the Later Zhou between 956 and 958 , and ceded all of Southern Tang 's land north of the Yangtze River .
With this , Southern Tang became the undisputedly most powerful regime in southern China .