China's debt is mostly internal, not external. It doesn't need a war to restructure debt. However, it does need to pay out an increasing amount of social pensions to its aging population, maintain its increasingly expensive and decreasingly utilized rail infrastructure, fund its growing state enterprises, and maintain its increasing military endeavors, etc. In other words, China's debt is owed to the citizens, but it now lacks the ability to pay them due to collapsing revenue from real estate.
It could try to print massively, but then its cash will be toilet paper, and for a country that mainly imports its resources, that would be devastating. So right now it's just printing quietly and in small doses.
War would make yuan worthless overnight.