(the Empire was giving way to the Republic), and Mexico, which under the long-term authoritarian rule of Porfirio Díaz had a special and deferential relationship with the United States. Leadership among the Latin American nations was exercised mainly by the Argentine delegation, in part because of the high caliber of its delegates, but also because Argentina saw U.S.-guided Panamericanism as a threat to her special relationship with key European countries. Argentine opposition began with the issue of electing the chairman of the Conference. The U.S. delegation more or less assumed that Blaine as host would be elected. But Blaine was technically not a delegate, and the Argentines (backed by the Chileans, who mistrusted Blaine because of his diplomatic role in the War of the Pacific) seized on this to argue that he was not qualified, and thus got the deliberations off to a sour start. In their sessions from 20 January to 27 April 1890 the delegates devoted much time to the issue of arbitration. There was considerable concern, eloquently voiced by the Argentine delegation, that the United States was seeking "hegemonic arbitration". There was also tension over question of whether military conquest could result in acquisition of sovereignty after a war. The specific concern was Chilean expansion at the expense of Peru and Bolivia in the War of the Pacific (1879–81). In the end the Conference failed to reach agreement on the establishment of an effective customs union, but was able to point with pride to a series of agreements on commercial and trade matters, as well as an arbitration agreement (albeit not as strong as the United States wished). However, the latter was never ratified, and the commercial agreements were limited by concern that they were too favorable to the United States. Almost hidden by the controversy over arbitration, conquest rights and customs unions was the conference's perhaps more significant achievement: the concept of regular inter-American meetings and the creation of permanent secretariat. The 14 April 1890 date of the founding of the secretariat, originally known as the International Bureau of American Republics, is celebrated as the "Day of the Americas" in recognition of the fact that the Bureau later became the Pan American Union and ultimately the present-day Organization of American States. Substantive issues of the Conference Fight over Blaine's presidency This was the first substantive matter taken up by the Conference, and it set the tone