A Chinese spy ship conducted a monthlong voyage that saw it sail around Japan's main islands as the United States ally held a large-scale military drill to bolster its defenses.

The Chinese Foreign Ministry did not immediately respond to a request for comment.

Why It Matters

China , which Japan views as a major threat , is expanding its military presence across the western Pacific Ocean through deployments of its navy—the world's largest by number of vessels—including missions that transited international straits near Japan .

Last month, Japan conducted a military exercise involving its air, ground and maritime branches across the country's main and outlying islands, as well as surrounding waters and airspace. The war game included a variety of training, including anti-shi

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