general principles for postal cooperation but failed to come to an agreement. The German victory in the Franco-Prussian War cleared away the obstacles to a postal union. After defeating Napoleon III in 1870, the North German Confederation and the South German states united to form the German Empire. The German Reichspost established a uniform set of postage rates and regulations for the new country, but the uniformity ended at the German border. Different amounts of postage were required to mail a letter from Berlin to New York, depending on which ship carried the letter across the Atlantic Ocean. To bring order to the system of international mail, German Postmaster-General Heinrich von Stephan called for another International Postal Congress in 1874. Meeting in Bern, Switzerland, the delegates agreed to all of von Stephan's proposals. The Treaty of Bern was signed on October 9, 1874, establishing what was then known as the General Postal Union. The treaty provided that: There should be a uniform flat rate to mail a letter anywhere in the world Postal authorities should give equal treatment to foreign and domestic mail Each country should retain all money it has collected for international postage. One important result of the Treaty was that it was no longer necessary to affix postage stamps of countries that a mailpiece passed through in transit. The UPU provides that stamps from member nations are accepted along the entire international route. Further developments The Treaty of Bern had been signed by 21 countries, 19 of which were located in Europe. After the General Postal Union was established, its membership grew rapidly as other countries joined. At the second Postal Union Congress in 1878, it was renamed the Universal Postal Union. French was the sole official language of the UPU until English was added as a working language in 1994. The majority of the UPU's documents and publications – including its flagship magazine, Union Postale – are available in the United Nations' six official languages French, English, Arabic, Chinese, Russian, and Spanish. Toward the end of the 19th century, the UPU issued rules concerning stamp design, intended to ensure maximum efficiency in handling international mail. One rule specified that stamp values be given in numerals, as denominations written out in letters were not universally comprehensible. Another required member nations to use the same colors on their stamps issued for post cards (green), normal letters (red) and