In January, 1864, the government of Peru issued invitations to all the governments of the Spanish nations of America to join in a congress to be held at Lima. The objects of the meeting as stated in the invitation were "to declare that the American nations represented in this congress form one single family," to improve postal facilities, to exchange statistical data, to provide for the settlement of all boundary disputes, and "to irrevocably abolish war, superseding it by arbitration, as the only means of compromising all misunderstandings and causes for disagreements between any of the South American republics." In accepting the invitation to the congress Colombia expressed the opinion that "the United States ought not to be invited, because their policy is adverse to all kind of alliances, and because the natural preponderance which a first-class power, as they are, has to exercise in the deliberations, might embarrass the action of the congress." So far as definite results were concerned, this congress at Lima was of no greater importance than its predecessors. The French invasion of Mexico and the war between Spain and the republics on the west coast of South America in 1865-66 brought about a realization of their danger on the part of the Spanish-American republics and a fuller appreciation of the friendship of the United States. In the war between Spain on the one hand and the allied republics of Peru, Chile, Bolivia, and Ecuador on the other, the United States declared its neutrality as usual, but at an early period of the struggle Secretary Seward offered to mediate between the warring nations. Spain refused to accept this offer, and the war dragged on in a state of "technical continuance" merely. The offer of mediation was again renewed by Secretary Fish, with the result that a conference was held at the State Department in 1870 attended by the representatives of Spain, Peru, Chile, and Ecuador. While it was found impossible to conclude a formal peace, the delegates signed an armistice April 11, 1871, by which the de facto suspension of hostilities was converted into an armistice which was to continue indefinitely and could not be broken by any of the belligerents without three years' notice, given through the government of the United States, of intention to renew hostilities.[276] Within ten years of the signature of this perpetual armistice, war broke out between Chile, on the one hand, and Peru and Bolivia, on the other (1879-83). The subject of dispute was the nitrate deposits of northern Chile. In 1880 Chile signed with Colombia an arbitration treaty which provided that in case the two parties should be unable in any given case to agree upon an arbitrator, the matter should be referred to the President of the United States. Article III of this treaty was as follows: