The People’s Liberation Army said naval, aerial, strategic-missile and other forces conducted joint training on Wednesday to the north, southwest and southeast of Taiwan in the run-up to the live-fire drills, which would involve the use of long-range weapons and conventional missiles.

While the designated live-fire zones mainly lie in international waters, some of them are close to Taiwan’s major ports and overlap with what Taipei claims as its territorial waters, which means the drills could disrupt civilian shipping. Depending on the launch sites and missile types, experts say the PLA projectiles could fly over Taiwan—a gesture that would be seen as a major escalation—on their way to waters east of the island.

Beijing’s response thus far hasn’t featured any direct use of force or resulted in any high-risk close encounters with other militaries—a risk that some observers had flagged ahead of Mrs. Pelosi’s trip. Even so, Western defense analysts said the show of force appears far more extensive than what China deployed during the 1995-1996 Taiwan Strait crisis, the tensest military standoff between Chinese and American forces in recent decades. That showdown, which featured Chinese missile firings and landing drills, was set off after Taiwan’s president traveled to the U.S.

“These announced exercises are not only unprecedented in scope but also likely in scale,” said M. Taylor Fravel, a professor and director of the MIT Security Studies Program at the Massachusetts Institute of Technology.