In the military use, combined operations , also known as joint operations, or interoperability capability, are either operations conducted by forces of two or more allied nations acting together for the accomplishment of a common strategy, a strategic and operational and sometimes tactical cooperation and interaction between units and formations of the Land, Naval and Air forces, or the cooperation between military and civilian authorities in peacekeeping or disaster relief operations.
The next development of combined operations 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.
In the South East Asia the development of combined operations proceeded along the same developmental path as in Europe with the raids by the Wokou, or so called 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).
The development in combined operations reached a new level when during the Crusades the element of political alliance was introduced as an influence on the military strategy, for example in the Sixth Crusade (1228 CE).
Although all combined operations 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 the scale of combined operations, 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).
The next development in the evolution of combined operations was made during the expansion of the European Empires and the era of colonialism that also led to the inclusion of the combined operations 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.
The period of the First World War that prolonged well past its completion into the 1920s saw combined operations established as a systematic and planned operations with larger scope then simple transportations of troops, 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 fo 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 combined 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 which for the first time saw the use of aircraft used in cooperation with the naval and land components of the deployed forces.
The phrase "combined operations" was first introduced by the British War Office in World War II to denote multi-service activities, those which involved air, land, or naval forces acting together, and coordinated by the Combined Operations Headquarters..
Given U.S. usage of the word 'joint' meaning such activities, the British usage faded relatively quickly. Post World War II the United States Department of Defense began using the phrase to denote multi-national operations, which might mean land forces of several countries, for example Combined Forces Land Component Command, or 'Combined Joint,' multi-national, multi-service activities and operations.
The phrase 'Combined Joint Task Force' then took on an extra meaning, beyond that of a multi-national, multi-service grouping, when it became a term used to describe a particular type of NATO deployment planning, outside the NATO Treaty area, in the late 1990s.
Since the early 1980s the concept of combined operations had been referred to by NATO and in particular by the United States Department of Defence as joint operations, as exemplified by the NATO Joint Operations Centre previously located in Kanne (Belgium) north of Fort Eben-Emael. The centre served to ensure interoperability and cooperation between the then 16 member states that has as of 2008 expanded to 26.
Regardless of the use of combined, joined or interoperability terms the concept is used to ensure that different military organisations maintain the ability to conduct combat and non-combat military operations regardless of the national and service (ground, naval and air forces) differences.
The ability to conduct combined operations allows national forces, their subordinated formations, units or systems to perform tasks and complete missions and operations together. The overriding requirement is that they share common doctrine and procedures, utilise each others' infrastructure and bases, and to be able to communicate with each other. These abilities reduce duplication of effort and increase economies of scale in a strategic alliance of its members, allow pooling of resources, and produces synergies among its commands.
In the NATO concept
interoperability does not necessarily require common military equipment. What is important is that this equipment can share common facilities and is able to communicate with other equipment.