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Expeditionary warfare is used to describe the organization of a state's military to fight abroad, especially when deployed to fight away from its established bases at home or abroad. Expeditionary forces were in part the antecedent of the modern concept of Rapid Deployment Forces. Traditionally, expeditionary forces were essentially self-sustaining with an organic logistics capability and with a full array of supporting arms.
Expeditions in the ancient world 
The earliest examples of expeditionary warfare come from the Sea Peoples, a term used for a confederacy of seafaring raiders of the second millennium BC who sailed into the eastern shores of the Mediterranean, caused political unrest, and attempted to enter or control Egyptian territory during the late 19th dynasty, and especially during Year 8 of Ramesses III of the 20th Dynasty.
The next exponents of expeditionary warfare in the ancient world of the Mediterranean Basin were the Carthaginians who introduced two entirely new dimensions to the use of naval forces by staging not only operations that combined naval and land troops, but also eventuated in combining strategic multi-national forces during the land phase of the operation when Hannibal in his most famous achievement at the outbreak of the Second Punic War marched an army, which included war elephants, from Iberia over the Pyrenees and the Alps into northern Italy.
Following on the example of Carthage, the Romans used expeditionary operations extensively to expand their Empire and influence in the Mediterranean and beyond, including the Roman conquest of Britain which was not only a limited expeditionary operation, but one conceived to include long-term occupation and Roman settlement of the territories.
Expeditionary warfare in the Dark Ages 
The most prominent development of expeditionary warfare during the European Middle Ages came from the environmental pressures in the Scandinavian region during the Middle Ages, and the emergence of the Viking migrations that combined raiding, longer term inland operations, occupation and settlement. These operations were conducted as sea, coastal and riverine operations, and sometimes were strategic in nature, reaching as far as Constantinople.
Crusader warfare 
The development in expeditionary operations reached a new level when during the Crusades the element of political alliance as an influence on the military strategy was introduced, for example in the Sixth Crusade (1228 CE).
Japanese piracy warfare 
Expeditionary warfare in Asia begun very much in the same way it had in the Mediterranean with short-term raids by Japanese pirates. Because the Wokou were weakly resisted by the Ming Dynasty, the raiding eventually developed into fully-fledged expeditionary warfare with the Japanese invasions of Korea (1592–1598).
Expeditionary warfare in the Age of Sail 
Although all expeditionary warfare until the invention of the combustion engine was largely dependent on the sailing vessels, it was with the creation of sophisticated rigging systems of the European Renaissance that the Age of Sail allowed a significant expansion in expeditionary warfare, notably by the European colonial empires. Some have argued that this was the first revolution in military affairs that changed national strategies, operational methods and tactics both at sea and on the land. One notable example of this evolution was the French Invasion of Egypt (1798).
Though a significantly expanded expeditionary operation, the Crimean War was the first example of a planned expeditionary campaign that was directed as part of a multinational coalition strategy. Aside from being the first modern expeditionary operation that used steam powered warships and telegraph communications which marked it as the departing point for the rest of the 19th and 20th century developments. It was also the first used as a military theatre instrument to force decision in the conflict, in what proved to be the last use of the sailing vessels in military expeditions.
European colonial expeditions 
Perhaps unique in the development of expeditionary warfare were the operations by Yermak during the Russian conquest of Siberia which was a largely land-based operation. This eventually led to the Russian settlement of the Far East and the coast of the Pacific Ocean.
The next development in the evolution of the expeditionary warfare was made during the expansion of the western European Empires and the era of colonialism that also led to the inclusion of the expeditionary methods into the direct expression of national strategies to avoid full-scale conflicts in the shape of the gunboat diplomacy approach. It was at this time that naval troops previously used almost exclusively for defence of vessels or minor beach operations were expanded to enable extended littoral operations. The colonial experience, though largely confined to the period before the First World War, persisted well into the 20th century.
Unique in this period was the emergence of non-empire building multinational (though not coalition) operations to defeat the Boxer Rebellion by the Eight-Nation Alliance that can be categorised as possibly the first peacekeeping operation in the modern era.
Perhaps the best example of the empire-building application of the expeditionary warfare were the conflicts between the British Empire and the Boer settlers in South Africa, and the resulting First and Second Boer Wars.
First World War 
The period of the First World War that prolonged well past its completion into the 1920s saw expeditionary warfare established as a systematic and planned type of operations with larger scope than simple transportations of troops to the theatre such as the British Expeditionary Force in 1914, Russian Expeditionary Force in 1916, and the American Expeditionary Force in 1917, and the beginnings of development in true combined operations at strategic, operational and tactical levels with the unsuccessful amphibious landing at Gallipoli. Not only did this operation combine the elements of overall war planning context, multinational deployment of forces as part of the same operation, and use of troops prepared for the landings (as opposed to disembarkation), as well as naval gunfire support that was only limited during the era of sailing ships, but also included extensive use of combat engineering in support of the infantry. One of the most extensive and complex of expeditionary operations that followed the war was the Allied intervention in the Russian Civil War that saw forces deployed in the Baltic region, the Arctic region, along the Black Sea coast, and in the Russian Far East.
Other expeditionary forces during WWI included:
- Australian Naval and Military Expeditionary Force
- First Australian Imperial Force
- Canadian Expeditionary Force 1914-1920
- New Zealand Expeditionary Force 1914-1918
Second World War 
- British Expeditionary Force
- China Expeditionary Army
- Italian Expeditionary Corps in Russia
- Brazilian Expeditionary Force
- Afrika Korps
- Second Australian Imperial Force
Modern era 
- American "power projection"
Expeditionary air warfare