China has been steadily intensifying military pressure on Taiwan over the past year, sending jets, drones, bombers and other planes farther and in greater numbers to extend an intimidating presence all around the island.

Chinese naval ships and air force planes have been edging closer to Taiwan’s territorial seas and skies, probing the island’s vigilance and trying to wear down its military planes and ships. Chinese forces have also been operating more frequently in skies and waters off the island’s eastern coast, facing the West Pacific. China’s increasing presence there signals its intent to dominate an expanse of sea that could be vital for the island’s defenses, including for securing potential aid from the United States in a conflict, experts say.

Beijing claims Taiwan is its lost territory that must accept unification, preferably peacefully, but by force if Chinese leaders deem that necessary. It has seized on moments of high tension with Taiwan to intensify military activities around the island, and it may put on another show of force in the coming days, when Taiwan’s vice president, Lai Ching-te, passes through the United States.