Universal Postal Union in the context of "Postcode"

The Republic of China (ROC) was established on 1 January 1912 as a sovereign state in mainland China following the 1911 Revolution, which overthrew the Manchu-led Qing dynasty and ended China's imperial history. From 1927, the Kuomintang (KMT) reunified the country and initially ruled it as a one-party state with Nanjing as the national capital. In 1949, the KMT-led government was defeated in the Chinese Civil War and lost control of the mainland to the Chinese Communist Party (CCP). The CCP established the People's Republic of China (PRC) while the ROC was forced to retreat to Taiwan; the ROC retains control over the Taiwan Area, and its political status remains disputed. The ROC is recorded as a founding member of both the League of Nations and the United Nations, and previously held a permanent seat on the United Nations Security Council until 1971, when the PRC took the seat of China from the ROC in the United Nations General Assembly Resolution 2758. It was also a member of the Universal Postal Union and the International Olympic Committee. The ROC claimed 11.4 million km (4.4 million sq mi) of territory, and its population of 541 million in 1949 made it the most populous country in the world.

The Republic of China was officially proclaimed on 1 January 1912 by revolutionaries under Sun Yat-sen, the ROC's founder and provisional president of the new republic, following the success of the 1911 Revolution. Puyi, the final Qing emperor, abdicated on 12 February 1912. Sun served briefly before handing the presidency to Yuan Shikai, the leader of the Beiyang Army. Yuan's Beiyang government quickly became authoritarian and exerted military power over the administration; in 1915, Yuan attempted to replace the Republic with his own imperial dynasty until popular unrest forced him to back down. When Yuan died in 1916, the country fragmented between local commanders of the Beiyang Army, beginning the Warlord Era defined by decentralized conflicts between rival cliques. At times, the most powerful of these cliques used their control of Beijing to assert claims to govern the entire Republic.

The Hellenic Post S.A. (Greek: Ελληνικά Ταχυδρομεία, abbreviated ΕΛΤΑ, ELTA) is the state-owned provider of postal services in Greece. It succeeded the former government Postal Service, founded in 1828. ELTA provides a universal postal service to all parts of Greece and is a member of the Universal Postal Union. Services provided include: letter post; parcel service; deposit accounts; Swiftpost, a nationwide next-day delivery service; and the EMS international express mail service.

The Treaty of Bern (formally the Treaty concerning the formation of a General Postal Union), signed on 9 October 1874, established the General Postal Union, which is today known as the Universal Postal Union. Named for the Swiss city of Bern, where it was signed, the treaty was the result of an international conference convened by the Swiss Government on 15 September 1874. It was attended by representatives of 22 nations. Plans for the conference had been drawn up by Heinrich von Stephan, Postmaster-General of the German Reichspost who demanded from the neutral Switzerland the organization of an International Postal Congress following the end of the French-German war of 1870–1871.

The purpose of the treaty was to unify disparate postal services and regulations so that international mail could be exchanged freely. The signatories of the treaty were the German Empire, Austria-Hungary, Belgium, Denmark, Egypt, Spain, the United States, France, Great Britain, Greece, Italy, Luxembourg, the Netherlands, Portugal, Romania, the Russian Empire, Serbia, the United Kingdoms of Sweden and Norway, Switzerland, and the Ottoman Empire.

Airmail (or air mail) is a mail transport service branded and sold on the basis of at least one leg of its journey being by air. Airmail items typically arrive more quickly than surface mail, and usually cost more to send. Airmail may be the only option for sending mail to some destinations, such as overseas, if the mail cannot wait the time it would take to arrive by ship, sometimes weeks. The Universal Postal Union adopted comprehensive rules for airmail at its 1929 Postal Union Congress in London. Since the official language of the Universal Postal Union is French, airmail items worldwide are often marked Par avion, literally: "by airplane".

For about the first half century of its existence, transportation of mail via aircraft was usually categorized and sold as a separate service (airmail) from surface mail. Today it is often the case that mail service is categorized and sold according to transit time alone, with mode of transport (land, sea, air) being decided on the back end in dynamic intermodal combinations. Thus even "regular" mail may make part of its journey on an aircraft. Such "air-speeded" mail is different from nominal airmail in its branding, price, and priority of service.