In a series of enactments, commencing with a joint resolution of May 1934, Congress sought to insulate the United States from the danger of involvement in foreign wars by embargoing the shipment of arms to foreign belligerents. The resolution mentioned enabled the President after consultation with the governments of other American Republics to proclaim that the prohibition of the sale of arms and munitions of war in the United States to those countries then engaged in armed conflict in the Chaco might contribute to the reestablishment of peace between those countries, after which it would become illegal to sell such material to the disputants or their agents.[319] On the same day that he signed the Chaco resolution, President Roosevelt issued the proclamation contemplated by the Act.[320] In August 1935 the embargo method was imposed uniformly without limitation as to area. The Neutrality Act of that year provided that if war broke out between two or more foreign states, the President should proclaim this fact, and thereafter it would be unlawful to export arms, ammunition or implements of war from any place in the United States, or its possessions to the belligerents, or to any neutral area for eventual trans-shipment to a belligerent country.[321] In addition, the Act placed a blanket prohibition upon the export or import of arms, except insofar as authorized under license procured from the National Munitions Control Board established by the Act.[322] When he had cause to believe a given ship was about to carry material to a belligerent, but the evidence was not deemed sufficient to justify forbidding the departure, the President could require the owner or commander to give a bond to the United States, with sufficient sureties, that the vessel would not deliver the men, or the cargo, or any part thereof to a belligerent.[323] Congress maintained a vigilant oversight over enforcement of its neutrality policy. Since the embargo authorized by the 1935 Act could be applied only on the occurrence of war between, or among, two or more foreign states, it could not be invoked in the Spanish Civil War. This situation Congress immediately rectified upon assembling in January 1937. Public Resolution No. 1, which became law on January 8, 1937, specifically prohibited the export of war material for use of either of the opposing forces in Spain.[324] Thereafter it amended the 1935 statute, retaining its provisions virtually intact, but directing it at instances of internecine as well as international war.[325] The same day that the President signed this law, he issued a proclamation finding that a state of civil strife unhappily existed in Spain and prohibited the direct or indirect export of material of war to either of the opposing armies.[326]