The British seized and searched the mails. United States officials below the rank of minister were searched by the British while traveling to and from the continent. Before the close of 1914, thirty-one cargoes of copper valued at $5,500,000 had been captured by Great Britain, but the United States owners were compensated. Their seizure, however, was illegal. Early in 1916, Germany agreed to give up the use of the submarine, but on condition that the United States make Great Britain obey international law. We could not force Great Britain to abide by international law, and consequently Germany resumed her submarine warfare in 1917, which was our official reason for entering the war. But this was only our legal excuse. The effective causes were our economic ties with the Allies, and Allied propaganda in the United States. We will examine these causes more carefully. Modern warfare is a conflict of economic resources as well as armies. The British navy cut off all economic intercourse between Germany and the United States. In this way, the economic resources of the United States were in the hands of the Allies. American agriculture, credit, and industry soon became indispensable to the Allied cause. In 1915 an Anglo-French mission came to New York and secured a loan of $500,000,000. This money was left with various banks in New York for the purpose of buying supplies from America. The Allied governments continued to borrow in Wall Street, and these banks loaned England and France money with which to buy materials. Soon the House of Morgan became the purchasing agent of the Allies. The Morgan firm selected Edward R. Stetinius, President of the Diamond Match Company, as the purchasing agent. Mr. Stetinius selected one hundred and seventy-five men to assist him in the task. They were soon purchasing supplies for the Allies at the rate of $10,000,000 a day. By September, 1917, the Morgan firm had purchased $3,000,000,000 in merchandise and munitions for the Allies in addition to the selling of Allied bonds. The day the United States declared war against Germany the British government's bank account with Morgan was heavily overdrawn. When Kitchener became Minister of War in Great Britain in 1915 one of his first acts was to cable Charles M. Schwab of the Bethlehem Steel Company to come to England immediately. Schwab went and agreed to sell all the output of the Bethlehem Steel Company to the British government. In less than two years, he shipped about $300,000,000 worth of war material to England. Twenty submarines were built and sent in parts to Canada where they were assembled and sent across to England. This was done a year before the German submarine _Deutschland_ came to the United States and was advertised as the first to cross the Atlantic. (See John Moody, "Masters of Capital," pages 162-172.)