North Yemen became independent of the Ottoman Empire in 1918. The British, who had set up a protectorate area around the southern port of Aden in the 19th century, withdrew in 1967 from what became South Yemen. Three years later, the southern government adopted a Marxist orientation. The massive exodus of hundreds of thousands of Yemenis from the south to the north contributed to two decades of hostility between the states. The two countries were formally unified as the Republic of Yemen in 1990. A southern secessionist movement and brief civil war in 1994 was quickly subdued.

In 2000, Saudi Arabia and Yemen agreed to a delimitation of their border. Fighting in the northwest between the government and the Huthis, a Zaydi Shia minority, began in 2004 and has since resulted in six rounds of fighting - the last ended in early 2010 with a cease-fire. The southern secessionist movement was revitalized in 2008 when a popular socioeconomic protest movement initiated the prior year took on political goals including secession.