Yemen has been at the crossroads of Africa, the Middle East and Asia for thousands of years thanks to its position on the ancient spice routes. It is one of the possible locations for the Biblical kingdom of Sheba.

The Romans knew this fertile country as Arabia Felix, in contrast to the relatively barren Arabia Deserta to the north.

The modern Republic of Yemen was born in 1990 when traditional North Yemen and communist South Yemen merged after years of clashes. Since unification Yemen has been slowly modernising and opening up to the world, but still retains much of its tribal character.

A short civil war in 1994 ended in defeat for separatist southerners, but regional tensions re-emerged in the summer of 2009 when government troops and Houthi rebels from the Shia Zaidi sect clashed in the north, killing hundreds and displacing more than a quarter of a million people.

Yemen was hit by more serious political upheaval early in 2011 when protesters - inspired by the Arab Spring uprisings in Tunisia and Egypt - rallied against the three-decades-old rule of President Saleh. He stepped down as part of a deal brokered by neighbouring countries at the end of the year, ushering in a transitional period of political reforms.

Al-Qaeda

In the meantime, Yemen had become a major base for Islamic militants after the crackdown on al-Qaeda closed their training bases in Afghanistan and Pakistan. The Yemeni branch of al-Qaeda was behind a failed attack on a US airliner on Christmas Day 2009, prompting greater government efforts to crush the insurgents.

A truce with the Houthi rebels in February 2010 allowed the government to focus on al-Qaeda and resurgent southern separatists, but the anti-government uprising in 2011 gave al-Qaeda a chance to establish several strongholds in Abyan province.

The precariousness of the government's hold on power was dramatically demonstrated in September 2014, when Houthi rebels swept into Sanaa and seized control of the capital.

Despite a UN-brokered peace deal that includes the formation of a new government, the Houthi forces have shown little sign of preparing to withdraw. They rejected a government-proposed constitution in January 2015 and the following month announced that they were setting up a transitional presidential council.

President Hadi fled to his home city of Aden in February, and in March Houthi forces began to advance on southern Yemen.
(BBC)