Question: When did the country where Apache helicopters are based in the nation that recently voted to leave a federal union join the European Community?

the european coal and steel community (ecsc) was an organisation of 6 european countries set up after world war ii to regulate their industrial production under a centralised authority. it was formally established in 1951 by the treaty of paris, signed by belgium, france, west germany, italy, the netherlands and luxembourg. the ecsc was the first international organisation to be based on the principles of supranationalism, and started the process of formal integration which ultimately led to the european union. <SEP> In a referendum on 23 June 2016, 51.9% of the participating UK electorate voted to leave the EU, out of a turnout of 72.2%. On 29 March 2017, the UK government invoked Article 50 of the Treaty on the European Union. The UK is thus due to leave the EU on 29 March 2019. <SEP> The leading example of the federal union of states is the European Union. Until recently, in the absence of prior agreement on a clear and precise definition, the concept was thought to mean (as a shorthand) 'a division of sovereignty between two levels of government'. New research, however, argues that this cannot be correct, as dividing sovereignty - when this concept is properly understood in its core meaning of the final and absolute source of political authority in a political community - is not possible. The descent of the United States into Civil War in the mid-nineteenth century, over disputes about unallocated competences concerning slavery and ultimately the right of secession, showed this. One or other level of government could be sovereign to decide such matters, but not both simultaneously. Therefore, it is now suggested that federalism is more appropriately conceived as 'a division of the powers flowing from sovereignty between two levels of government'. What differentiates the concept from other multi-level political forms is the characteristic of equality of standing between the two levels of government established. This clarified definition opens the way to identifying two distinct federal forms, where before only one was known, based upon whether sovereignty resides in the whole (in one people) or in the parts (in many peoples): the federal state (or federation) and the federal union of states (or federal union), respectively. Leading examples of the federal state include the United States, Germany, Canada, Switzerland, Australia and India. <SEP> The 1960s and 1970s saw an acceleration in the decolonisation of Africa and the Caribbean. Over 20 countries gained independence from Britain as part of a planned transition to self-government. As Britain's ties to its former empire weakened, the British government sought entry to the European Community, a goal it achieved in 1973. In 1965, however, the Rhodesian Prime Minister, Ian Smith, in opposition to moves toward majority rule, declared unilateral independence from Britain while still expressing "loyalty and devotion" to Elizabeth. Although the Queen dismissed him in a formal declaration, and the international community applied sanctions against Rhodesia, his regime survived for over a decade. <SEP> The Army Air Corps (AAC) is a component of the British Army, first formed in 1942 during the Second World War by grouping the various airborne units of the British Army (which are no longer part of the AAC). Today, there are eight regiments (7 Regular Army and 1 Reserve) of the AAC as well as four Independent Flights and two Independent Squadrons deployed in support of British Army operations across the world. They are located in Britain, Brunei, Canada, and Germany. Some AAC squadrons provide the offensive and air assault elements of 16 Air Assault Brigade through Joint Helicopter Command. <SEP> switzerland joined the council of europe in 1963. in 1979 areas from the canton of bern attained independence from the bernese, forming the new canton of jura. on 18 april 1999 the swiss population and the cantons voted in favour of a completely revised federal constitution.in 2002 switzerland became a full member of the united nations, leaving the vatican city as the last widely recognised state without full un membership. switzerland is a founding member of the efta, but is not a member of the european economic area. an application for membership in the european union was sent in may 1992, but not advanced since the eea was rejected in december 1992 when switzerland was the only country to launch a referendum on the eea. there have since been several referendums on the eu issue; due to opposition from the citizens, the membership application has been withdrawn. nonetheless, swiss law is gradually being adjusted to conform with that of the eu, and the government has signed a number of bilateral agreements with the european union. switzerland, together with liechtenstein, has been completely surrounded by the eu since austria's entry in 1995. on 5 june 2005, swiss voters agreed by a 55% majority to join the schengen treaty, a result that was regarded by eu commentators as a sign of support by switzerland, a country that is traditionally perceived as independent and reluctant to enter supranational bodies.