As Kurds plan to declare a federal region in northern Syria, they hope to both cement their control of the area and be a major player in whatever central government emerges from the five-year civil war.

Federations throughout history have been both long-lasting, like Switzerland and the United States, and short-lived, acrimonious experiments, like Iraq after the U.S.-led invasion of 2003.

The system relies on self-governing regions unifying under a common, central administration. But some have fallen quickly apart under ethnic, religious or cultural strains.

A look at some federations and national partitions in recent history and how they have fared:

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BOSNIA — The former Yugoslavia erupted into a civil war in the 1990s. The Bosnian federation formula — imposed primarily by the U.S. — ended the fighting. It divided Bosnia into two entities, the Muslim-Croat and the Bosnian-Serb, and no decision can be made on the federal level without the consent of all three Bosnian ethnic groups — Bosniak Muslims, Catholic Croats and Christian Orthodox Serbs. But deep distrust remains, even 20 years after the war ended.

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CYPRUS — A 1974 Turkish invasion triggered by a coup cleaved Cyprus along ethnic lines, with a breakaway Turkish Cypriot state in the island's north. Cyprus joined the European Union in 2004, but only the internationally recognized south enjoys full membership benefits. The two sides are in talks to reunify the island as a "bizonal, bicommunal federation," meaning a Turkish-Cypriot-administered zone and a Greek- Cypriot one, overseen by a central federal government.

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IRAQ — Iraq's 2005 constitution, drafted after the U.S.-led invasion that toppled Saddam Hussein, calls for a federal system and includes provisions for the creation of self-rule regions. While various parts of Iraq have considered setting up autonomous areas, the Kurds in northern Iraq are the only ones to have such an arrangement. They enjoy considerable autonomy, have their own flag and are secured by a Kurdish military force known as the peshmerga, which has received extensive U.S. support and is battling Islamic State militants.

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IRELAND — Ireland's Catholic south launched a war of independence from the United Kingdom in 1919. British Protestants demanded their own northern state, and Britain created a U.K. region called Northern Ireland in 1921. Months later, Britain and southern rebel leaders struck a treaty creating an Irish Free State that survived a 1922-23 civil war. That state evolved into a peaceful Republic of Ireland. Northern Ireland suffered rising bloodshed from the late 1960s as the outlawed Irish Republican Army tried to force the territory into the republic, but Northern Ireland's 1998 peace accord reaffirmed its U.K. status and most IRA members renounced violence in 2005.

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NIGERIA — Africa's most populous nation became a federation in 1963, just a few years after British colonialists handed over the country. But allegations over northern dominance and graft saw its first military coup in 1966, setting the stage for the breakaway of Biafra and the civil war that killed 1 million people. Nigeria remains a democratic federation, but has suffered from a weak central government.

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PALESTINIAN TERRITORIES — The idea of a federation between Jordan and Palestinian territories has been repeatedly raised, though largely put aside by the late 1980s over the lack of a Palestinian state. Israel captured the West Bank and east Jerusalem from Jordan and the Gaza Strip from Egypt in the 1967 war and it has been a long-standing Palestinian demand to establish a state in all three areas.

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SOUTH SUDAN — South Sudan, which formed out of part of Sudan in 2011, descended into violence in 2013 when a fight among the security forces in the capital, Juba, boiled over into a rebellion. Despite a peace agreement signed in August 2015, there have been occasional clashes between government forces and rebels. Tens of thousands have died and at least 2 million have been displaced from their homes, while politicians and leaders struggle to determine the country's federal character.

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Associated Press writers Karin Laub in Amman, Jordan; Mohammad Daraghmeh in Ramallah, West Bank; Menelaos Hadjicostis in Nicosia, Cyprus; Dusan Stojanovic in Belgrade, Serbia; Shawn Pogatchnik in Dublin, Ireland; and Adam Schreck contributed to this report.

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Follow Jon Gambrell on Twitter at www.twitter.com/jongambrellap.