OVERALL DEFINITION
In its purist form, a “dead country” is a nation or political entity which no longer exists. My definition of a “dead country” is essentially any political, colonial, military or revolutionary entity which has issued at least one stamp used for postage and/or a unit of paper money accepted as legal currency. For my collection, I limit the “countries included” to those that ceased to exist as a defined entity before 1960. Primarily because I wanted to limit my personal collection to older stamps.

WHAT CONSTITUTES THE “END” OF A COUNTRY, POLITICAL ENTITY, REVOLUTION, OCCUPATION OR COLONY
Deciding what constitutes the end of a country is important in defining exactly what is a “dead country”. As I continue to study each area and its history, these definitions will continue to be refined as I develop a workable set of criteria for when a country “ends” and when another starts. My definition of the “end” doesn’t necessarily begin (or even end) the name of the country involved. For instance, the occupation of Belgium by German forces in World War 1 did not start, nor end the nation of Belgium. But the occupation period is a “dead country” when control by Germany was exerted, and postage stamps or currency was issued for that period. The same could be said about a failed revolution. The following are some of the criteria for when a country becomes “dead”:

• Overthrow of a absolute monarchy style government (not merely a dynasty)
• Overthrow or withdrawal of colonial rule
• Annexation of a country into a larger country
• The start or end of a “transitional government”
• Joining of two or more political entities
• Change of political control of an outside entity
• Occupation by an external entity
• Defeat or withdrawal of occupational forces

CATEGORIES OF POLITICAL ENTITIES

Empires – A single supreme authority which has an extensive group of states or countries under its authority (e.g. Imperial Russia, the Austro-Hungary Empire, the German Empire or the Ottoman Empire)
Empires – A single supreme authority which has an extensive group of states or countries under its authority (e.g. Imperial Russia, the Austro-Hungary Empire, the German Empire or the Ottoman Empire)
Nations – An independent, self-governed sovereign nation (e.g. Hawaii, Hejaz or Orange Free State)
City States – An autonomous city, which existed as a sovereign nation (e.g. Danzig, Hamburg, or Bremen)
Resurrected Countries – An independent country which ceased to exist for more than 40 years, and later rose again (e.g. Lithuania, Georgia or Armenia)
Semi-Autonomous States – A state with limited autonomy under the control of an empire or larger country. (e.g. India Princely States, Grand Duchy of Finland or Buenos Aries)
Colonies – A territory separated, but subject to a distant ruling power (e.g. Obock, Kiauchau, or Cape Colony)
Puppet States – A “country” proclaimed to be an independent nation, but in reality was controlled by a another government (e.g. Manchukuo, Italian Social Republic and Bohemia and Moravia)
Military Occupations – A nation or territory occupied and controlled by foreign military forces (e.g. Burshire, Japanese Occupation of Malaya, or the Allied Occupation of Baden)
League of Nations Mandates – Territories from the defeated Ottoman and German Empires after WW1, which were given to allies nations to administer by the League of Nations (e.g. Palestine, Tanganyika, or the Territory of New Guinea)
International Zones – Territories under a broad International control and administration (e.g. Tangier International Zone and West Berlin)
Plebiscite Regions – A treaty of Versailles region where a vote was taken by the local population to determine national alignment (e.g. Upper Silesia, Marienwerder or Allenstein)
Revolutionary Entities – A revolutionary government, army or group formed by locals that tried to overthrow, radically change or separate from an existing country. The entity counts whether or not it was successful (e.g. Confederate States of America, Theriso Revolution in Crete, Autonomous Republic of Epirus)
Government is Exile – A legitimate government of a country is operating remotely, as its country is occupied by a foreign power. The legitimacy needs to be recognized by a portion of the international community. Over time, the government can lose legitimacy based on international recognition (e.g. Polish Government in Exile, WW2)

There are some types I am still thinking about

For Stamp Collectors, the following are NOT included in my definition of a Country

Name Changes – Countries where only the name changed without a substantial change in government are not included (e.g. Ceylon to Sri Lanka, Persia to Iran and Siam to Thailand)
Private Issuers of Stamps – Private, non governmental or military issuers are not included (Baena, Danube Steam Navigation Company or Niklasdorf). Special note: private banks which issued currency legal in that country are included
Siege Issues – Stamps issued for use during a military siege.
Concentration Camp Issues – Stamps issued for use during a military siege.
Postmarks only – To be included, the entity must have issued at least one unique stamp or banknote. The rationale is that I am interested in country history, not necessarily postal history.
Local / Provisional Issues – Local entities issuing stamps as a stop-gap due to interruption of postal services without any higher aspirations are not included (e.g. Canary Islands, Kilis, Mafeking siege issues or Carupano).

As I continue to examine my definitions, I welcome comments and suggestions of how to make them more consistent and accurate.