North Korea¡¯s growing missile arsenal might be the most obvious and immediate military threat facing Japan, but defense planners in Tokyo are focused on a much larger and more challenging foe as they prepare for the years ahead.

China has stepped up military spending and already dominates the South China Sea, through which Japan¡¯s trade with major markets, including Europe and the Middle East, flows.

Now, Japanese military experts are worried Beijing may be on the brink of opening access to the Pacific through a Japanese island chain that has marked the limit of China¡¯s military influence for decades.