Anticipating War with China, the US Air Force Is Fanning Out Across the Pacific

There's no need for a specific scenario. The military only needs to know how they're going to fight a war, not why. The why is left to politicians who decide whether to deploy the military or not, and set the budget in anticipation of potentially needing to deploy it in the future.

I don't know why the media you consume focus on the effect before the cause has been determined. Maybe you should stop paying attention to them.

I would suppose conflict over Taiwan is high on the possible scenario list, though personally I think its not super likely.

Taiwan aside, the Chinese are very aggressively trying to expand their sphere of influence through the South China Sea and into the Pacific. Things like them sending huge 'fishing fleets' into other territories which are allegedly armed ( 1 ) and building naval bases in the Atlantic and Pacific ( 2 ) are obvious signs of this, as well as the Chinese government turning a blind eye to large scale poaching in other countries waters. What could potentially happen is a collision on the sea which would raise tensions, or a diplomatic dispute arising if a nation decides to sink a ship full of Chinese nationals. The political posturing from both the US and the Chinese in the last few years suggest that it wouldn't be too unlikely that a difficult situation like those could become a small scale shooting war.

1. https://www.bbc.com/news/world-asia-56474847

2. https://www.defensenews.com/opinion/commentary/2020/04/17/ch...