From Citizendium, the Citizens' Compendium
A secret plan developed at the request of U.S. Secretary of State William L. Marcy by U.S. European diplomats James Buchanan, John Y. Mason, and Pierre Soulé in 1854 at Ostend, Belgium. The plan called for the acquisition (either by purchase or invasion) of Cuba by the United States. The document was filled with pro-slavery pronouncements (written mainly by Soulé). It was leaked to the press, after which Marcy denounced any involvement with it.