I found this last week. The Rand Corp did a sort of table top exercise that engaged China and Taiwan. I summed up the 130 pages briefly below. https://www.rand.org/pubs/research_reports/RRA739-4.html Keep your eyes out for things that prop this up. US defending Japan against a major Chinese attack would likely require maintaining some forward-deployed U.S. naval forces and pre-positioned materiel in the Asia-Pacific. Given China's ability to target bases and ports, the United States would still need access to a large number of wartime operating locations in partner countries to increase the survivability of its forces involved in the defense of Japan. China Attacks Japan’s Armed Forces and Economy PLA Attacks on Japan After Occupying Taiwan, China Seizes the Southern Ryukyu Islands PLA Approach to Seizing the Southern Ryukyus. Japanese and U.S. Approaches IThe United States Imposes a Distant Blockade on China During a War Between China and Japan