China has given the impression that they are willing to force Taiwan to become part of China by force.
China is building up a large, modern military. They have converted a number of atols in the South China sea into military bases.
China just finished a modern aircraft carrier that can complete with anything that the US can field. China is also building modern fighters.
Recent published satillite photos show China constructint a large number of nuclear nuclear missile silos. China has an advanced nuclear weapons program (see the book Nuclear Express).
China has a long history of resentment regarding the way they were treated by the colonial powers. They want recognition as a first class world power and this includes military power.
China is also famously active in cyberwarfare.
This is not a picture of a country that is nothing but benevolence.
All this said: I cannot imagine a serious military conflict with China.
I recently moved into a new house and purchased items for the house. The vast majority of the itemes were made in China. How does a country have a military conflict with a country that supplies the majority of items they consume. From the Chinese side, how does a country have a serious military conflict with one of its major customers?
Unfortunately, people are not always rational. Putin has set Russia back twenty years. Perhpas Zi Jinping's search for Chinese greatness could result in something equally stupid.
Without a doubt this is the Asian century and China is a harbinger of this change.
I wish that people would just behave. Competition between the US and China is one thing. But actually serious conflict, especially military conflict is just crazy.