As China girds for a deepening global rivalry with the United States, Beijing is testing how far its navy can operate from home, and how well its warships can work together on the open seas. In recent exercises involving two aircraft carriers, China gave a bold display of how it seeks to assert dominance in the western Pacific.

From late May and for much of June in seas near Japan, the two Chinese carriers — the Liaoning and the Shandong — practiced takeoffs and landings of fighter jets and helicopters, as many as 90 or more times on some days, according to reports from the Japanese military’s joint staff. Each carrier was protected by several warships.

The exercises, which caused Japan to express “serious concerns,” were a template for how China could use a growing collection of aircraft carriers to project armed power into the Pacific and try to overawe Asian neighbors aligned with Washington.

This was the first time that two Chinese carriers had ventured together past the “first island chain” — the barrier of islands east of China that includes the Japanese island of Okinawa, where U.S. Marines are based, and Taiwan — and toward Guam, a U.S. military hub, said Christopher Sharman, the director of the China Maritime Studies Institute at the U.S. Naval War College. Guam is part of what is called the “second island chain,” which stretches from Tokyo to south of Palau.

The Chinese naval activities near or past the second island chain signal that U.S. forces “operating in the vicinity of Guam could be at greater risk,” Mr. Sharman said.