Held at the Memorial Continental Hall (now DAR Constitution Hall) in downtown Washington, it resulted in three major treaties: Four-Power Treaty, Five-Power Treaty (more commonly known as the Washington Naval Treaty) and the Nine-Power Treaty and a number of smaller agreements. These treaties preserved peace during the 1920s but are also credited with enabling the rise of the Japanese Empire as a naval power leading up to World War II.
For the American delegation, led by Secretary of State Charles Evans Hughes, the primary objective of the conference was to inhibit Japanese naval expansion in the waters of the west Pacific, especially with regard to fortifications on strategically valuable islands. Their secondary objectives were intended to ultimately limit Japanese expansion, but also to alleviate concerns over possible antagonism with the British. They were: first, to eliminate Anglo-American tension by abrogating the Anglo-Japanese alliance; second, to agree upon a favorable naval ratio vis-à-vis Japan; and, third, to have the Japanese officially accept a continuance of the Open Door policy in China.
The British, however, took a more cautious and tempered approach. Indeed, British officials brought certain general desires to the conference—to achieve peace and stability in the western Pacific, avoid a naval arms race with the United States, thwart Japanese encroachment into areas under their influence, and preserve the security of Singapore, Hong Kong, and Dominion countries—but they did not enter the conference with a specific laundry list of demands; rather, they brought with them a vague vision of what the western Pacific should look like after an agreement.
Japanese officials were more focused on specifics than the British, and approached the conference with two primary goals: first, to sign a naval treaty with Britain and the United States, and, secondly, to obtain official recognition of Japan’s special interests in Manchuria and Mongolia. Japanese officials also brought other issues to the conference—a strong demand that they remain in control of Yap, Siberia, and Tsingtao, as well as more general concerns about the growing presence of American fleets in the Pacific.
The American hand was strengthened by the interception and decryption of secret instructions from the Japanese government to its delegation. The message revealed the lowest naval ratio that would be acceptable to Tokyo; U.S. negotiators used this knowledge to push the Japanese to it. This success, one of the first in the U.S. government's budding eavesdropping and cryptology efforts, led eventually to the growth of such agencies.