In the early autumn of September, the Heilongjiang River is mild in climate and moderate in water levels, making it the most suitable time of the year for navigation. In the past, when the Nurgan Metropolitan Authority was still in existence, the Ming Army would seize this best month to conduct official ship inspections and transport supplies. Large official ships carrying food, weapons, and daily necessities would sail down the Great River, heading to the mid-to-lower reaches of the entire Heilongjiang River, becoming the most critical lifeline for maintaining the garrisons of Outer Northeast.
