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How did the Black Ships pressure Japan to open its ports to foreign trade?

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Map showing the territorial expansion of the Japanese Empire from 1870 to 1942 across East and Southeast Asia and the Pacific. The map uses color codes to indicate the original Japanese territory in 1870, subsequent acquisitions, and the farthest extent of Japanese occupation and conquest by 1942, including parts of China, Korea, Manchuria, Southeast Asia, and numerous Pacific islands. An inset map displays the broader reach of Japanese control at its peak. — Empire of Japan The Empire of Japan, 1870–1942.

The "Black Ships" were a squadron of U.S. warships commanded by Commodore Matthew C. Perry, whose arrival in 1853 effectively ended Japan’s two centuries of isolation.12

Perry utilized a strategy of "gunboat diplomacy" to pressure the Japanese government. Upon entering Uraga Harbor in July 1853, he displayed superior naval force and maintained a "resolute attitude," refusing to leave until he had delivered a letter from the U.S. President requesting a treaty. He threatened to deliver the documents by force if necessary, and the Japanese, recognizing that their own armaments were inadequate to resist such technologically advanced warships, chose to accept the letter to stall for time while they bolstered their defenses.13

Aware of China’s recent defeat by Western powers in the Opium War, the Japanese government realized they could not maintain their traditional seclusion policy against such military pressure. When Perry returned in 1854 with an even larger fleet, the Japanese agreed to sign the Treaty of Kanagawa, which opened specific ports to U.S. ships and established diplomatic relations.123