Yemen, officially the Republic of Yemen, is a country in West Asia. Including the Socotra Archipelago, mainland Yemen is located in southern Arabia; bordering Saudi Arabia to the north, Oman to the northeast, the south-eastern part of the Arabian Sea to the east, the Gulf of Aden to the south, and the Red Sea to the west, sharing maritime borders with Djibouti, Eritrea, and Somalia across the Horn of Africa. Covering roughly 455,503 square kilometres (175,871 square miles), with a coastline of approximately 2,000 kilometres (1,200 miles), Yemen is the second largest country on the Arabian Peninsula. Sanaa is its constitutional capital and largest city. Yemen's estimated population is 34.7 million, mostly Arab Muslims. It is a member of the Arab League, the United Nations, the Non-Aligned Movement and the Organisation of Islamic Cooperation.
Owing to its geographic location, Yemen has been at the crossroads of many civilisations for over 7,000 years. The Sabaeans formed a thriving commercial kingdom that influenced parts of modern Ethiopia and Eritrea. In 275 CE, it was succeeded by the Himyarite Kingdom, which spanned much of Yemen's present-day territory and was heavily influenced by Judaism. Christianity arrived in the fourth century, followed by the rapid spread of Islam in the seventh century. From its conversion to Islam, Yemen became a center of Islamic learning, and Yemenite troops played a crucial role in early Islamic conquests. Much of Yemen's architecture survived until modern times. For centuries, it was a primary producer of coffee, exported through the port of Mocha. Various dynasties emerged between the 9th and 16th centuries. During the 19th century, the country was divided between the Ottoman and British empires. After World War I, the Kingdom of Yemen was established, which in 1962 became the Yemen Arab Republic (North Yemen) following a civil war. In 1967, the People's Democratic Republic of Yemen (South Yemen) gained its independence from the British Aden Protectorate, becoming the first and only communist state in the Middle East and the Arab world. In 1990, the two Yemeni states united to form the modern Republic of Yemen, with Ali Abdullah Saleh serving as the first president until his resignation in 2012 in the wake of the Arab Spring.