Question: Who ruled the country known for its populations of Muslims, and the people who traded slaves into the Middle East, before it was conquered by the followers of Muhammad?

full_context: Document 1: Guinea-Bissau: Portuguese natives comprise a very small percentage of Guinea-Bissauans. After Guinea-Bissau gained independence, most of the Portuguese nationals left the country. The country has a tiny Chinese population. These include traders and merchants of mixed Portuguese and Chinese ancestry from Macau, a former Asian Portuguese colony.
Document 2: Syria: Syria (Arabic: سوريا ‎ Sūriyā), officially known as the Syrian Arab Republic (Arabic: الجمهورية العربية السورية ‎ al - Jumhūrīyah al - ʻArabīyah as - Sūrīyah) is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the west, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest. Syria's capital and largest city is Damascus. A country of fertile plains, high mountains, and deserts, Syria is home to diverse ethnic and religious groups, including Syrian Arabs, Greeks, Armenians, Assyrians, Kurds, Circassians, Mandeans and Turks. Religious groups include Sunnis, Christians, Alawites, Druze, Isma'ilis, Mandeans, Shiites, Salafis, Yazidis, and Jews. Sunni make up the largest religious group in Syria.
Document 3: Syria: Sunni Muslims make up between 69–74% of Syria's population and Sunni Arabs account for 59–60% of the population. Most Kurds (8.5%) and most Turkoman (3%) are Sunni and account for the difference between Sunnis and Sunni Arabs, while 13% of Syrians are Shia Muslims (particularly Alawite, Twelvers, and Ismailis but there are also Arabs, Kurds and Turkoman), 10% Christian (the majority are Antiochian Greek Orthodox, the rest are Syrian Orthodox, Greek Catholic and other Catholic Rites, Assyrian Church of the East, Armenian Orthodox, Protestants and other denominations), and 3% Druze. Druze number around 500,000, and concentrate mainly in the southern area of Jabal al-Druze.President Bashar al-Assad's family is Alawite and Alawites dominate the government of Syria and hold key military positions. In May 2013, SOHR stated that out of 94,000 killed during the Syrian Civil War, at least 41,000 were Alawites.Christians (2.5 million), a sizable number of whom are found among Syria's population of Palestinian refugees, are divided into several sects: Chalcedonian Antiochian Orthodox make up 45.7% of the Christian population; the Catholics (Melkite, Armenian Catholic, Syriac Catholic, Maronite, Chaldean Catholic and Latin) make up 16.2%; the Armenian Apostolic Church 10.9%, the Syriac Orthodox make up 22.4%; Assyrian Church of the East and several smaller Christian denominations account for the remainder. Many Christian monasteries also exist. Many Christian Syrians belong to a high socio-economic class.
Document 4: Religion in Kyrgyzstan: Islam is the most widely held faith. Official sources estimated that 87,6 percent of the population is Muslim. The CIA World Factbook estimates 85%. Almost all the Muslims are Sunni; there are few Shia in the country (approximately one thousand). There are also a few Ahmadiyya Muslims, though unrecognised by the country. According to SARA, as of May 2007 there were 1,650 mosques, of which 1,623 were registered. There also were seven institutes for higher Islamic teaching.
Document 5: Religion in Lebanon: Lebanon has several different main religions. The country has the most religiously diverse society of all states within the Middle East, comprising 18 recognized religious sects. The main two religions are Islam (Shia and Sunni) with 54% of followers and Christianity (the Maronite Church, the Greek Orthodox Church, the Melkite Greek Catholic Church, the Protestant Church, the Armenian Apostolic Church) with 40.4% of followers. There is also the Druze minority religion, which under the Lebanese political division (Parliament of Lebanon Seat Allocation) the Druze community is designated as one of the five Lebanese Muslim communities (Sunni, Shia, Druze, Alawi, and Ismaili).
Document 6: Guinea-Bissau: Guinea-Bissau is a member of the United Nations, African Union, Economic Community of West African States, Organisation of Islamic Cooperation, the Latin Union, Community of Portuguese Language Countries, La Francophonie and the South Atlantic Peace and Cooperation Zone.
Document 7: Umayyad Caliphate: Early Muslim armies stayed in encampments away from cities because Umar feared that they might get attracted to wealth and luxury. In the process, they might turn away from the worship of God and start accumulating wealth and establishing dynasties. When Uthman ibn al-Affan became very old, Marwan I, a relative of Muawiyah I, slipped into the vacuum, became his secretary, slowly assumed more control and relaxed some of these restrictions. Marwan I had previously been excluded from positions of responsibility. In 656, Muhammad ibn Abi Bakr, the son of Abu Bakr, the adopted son of Ali ibn Abi Talib, and the great grandfather of Ja'far al-Sadiq, showed some Egyptians the house of Uthman ibn al-Affan. Later the Egyptians ended up killing Uthman ibn al-Affan.
Document 8: Umayyad Caliphate: The Umayyads have met with a largely negative reception from later Islamic historians, who have accused them of promoting a kingship (mulk, a term with connotations of tyranny) instead of a true caliphate (khilafa). In this respect it is notable that the Umayyad caliphs referred to themselves not as khalifat rasul Allah ("successor of the messenger of God", the title preferred by the tradition), but rather as khalifat Allah ("deputy of God"). The distinction seems to indicate that the Umayyads "regarded themselves as God's representatives at the head of the community and saw no need to share their religious power with, or delegate it to, the emergent class of religious scholars." In fact, it was precisely this class of scholars, based largely in Iraq, that was responsible for collecting and recording the traditions that form the primary source material for the history of the Umayyad period. In reconstructing this history, therefore, it is necessary to rely mainly on sources, such as the histories of Tabari and Baladhuri, that were written in the Abbasid court at Baghdad.
Document 9: Central African Republic: During the 16th and 17th centuries slave traders began to raid the region as part of the expansion of the Saharan and Nile River slave routes. Their captives were slaved and shipped to the Mediterranean coast, Europe, Arabia, the Western Hemisphere, or to the slave ports and factories along the West and North Africa or South the Ubanqui and Congo rivers. In the mid 19th century, the Bobangi people became major slave traders and sold their captives to the Americas using the Ubangi river to reach the coast. During the 18th century Bandia-Nzakara peoples established the Bangassou Kingdom along the Ubangi River.
Document 10: Umayyad Caliphate: After the assassination of Uthman in 656, Ali, a member of the Quraysh tribe and the cousin and son-in-law of Muhammad, was elected as the caliph. He soon met with resistance from several factions, owing to his relative political inexperience. Ali moved his capital from Medina to Kufa. The resulting conflict, which lasted from 656 until 661, is known as the First Fitna ("civil war"). Muawiyah I, the governor of Syria, a relative of Uthman ibn al-Affan and Marwan I, wanted the culprits arrested. Marwan I manipulated everyone and created conflict. Aisha, the wife of Muhammad, and Talhah and Al-Zubayr, two of the companions of Muhammad, went to Basra to tell Ali to arrest the culprits who murdered Uthman. Marwan I and other people who wanted conflict manipulated everyone to fight. The two sides clashed at the Battle of the Camel in 656, where Ali won a decisive victory.
Document 11: Guinea-Bissau: Guinea-Bissau was once part of the kingdom of Gabu, part of the Mali Empire; parts of this kingdom persisted until the 18th century. Other parts of the territory in the current country were considered by the Portuguese as part of their empire. Portuguese Guinea was known as the Slave Coast, as it was a major area for the exportation of African slaves by Europeans to the western hemisphere. Previously slaves had been traded by Arabs north to the northern part of Africa and into the Middle East.
Document 12: Umayyad Caliphate: The Umayyad caliphate was marked both by territorial expansion and by the administrative and cultural problems that such expansion created. Despite some notable exceptions, the Umayyads tended to favor the rights of the old Arab families, and in particular their own, over those of newly converted Muslims (mawali). Therefore, they held to a less universalist conception of Islam than did many of their rivals. As G.R. Hawting has written, "Islam was in fact regarded as the property of the conquering aristocracy."
Document 13: Guinea-Bissau: Guinea-Bissau was once part of the kingdom of Gabu, as well as part of the Mali Empire. Parts of this kingdom persisted until the 18th century, while a few others were under some rule by the Portuguese Empire since the 16th century. In the 19th century, it was colonized as Portuguese Guinea. Upon independence, declared in 1973 and recognised in 1974, the name of its capital, Bissau, was added to the country's name to prevent confusion with Guinea (formerly French Guinea). Guinea-Bissau has a history of political instability since independence, and no elected president has successfully served a full five-year term.
Document 14: Umayyad Caliphate: The Quran and Muhammad talked about racial equality and justice as in The Farewell Sermon. Tribal and nationalistic differences were discouraged. But after Muhammad's passing, the old tribal differences between the Arabs started to resurface. Following the Roman–Persian Wars and the Byzantine–Sassanid Wars, deep rooted differences between Iraq, formally under the Persian Sassanid Empire, and Syria, formally under the Byzantine Empire, also existed. Each wanted the capital of the newly established Islamic State to be in their area. Previously, the second caliph Umar was very firm on the governors and his spies kept an eye on them. If he felt that a governor or a commander was becoming attracted to wealth, he had him removed from his position.
Document 15: Religion in Syria: In Syria, Jews of both origins, numbering altogether fewer than 3,000 in 1987, are found. After a mass emigration in 1992, today fewer than 200 Jews live in Syria, mostly in the capital. Syrian Jews are Arabic-speaking and barely distinguishable from the Arabs around them. In Syria, as elsewhere, the degree to which Jews submit to the disciplines of their religion varies.
ground_truth: Byzantine Empire
sub_queries: Who traded slaves into the Middle East? Answer: Arabs
What country is known for its Arabs and Muslims? Answer: Syria
Who ruled Syria before it was conquered by the followers of Muhammad? Answer: Byzantine Empire