Chattel slavery existed in the Trucial States (1892–1971), which later formed the United Arab Emirates. The Trucial States consisted of the Sheikdoms Dubai, Abu Dhabi, Sharjah, Ajman, Umm Al Quwain, Fujairah, and Ras Al Khaimah.
The region was mainly supplied with enslaved people from the Indian Ocean slave trade, but humans were also trafficked to the area from Hejaz, Oman and Persia. Slaves were used in the famous pearl fish industry and later in the oil industry, as well as sex slaves and domestic servants. Many members of the Afro-Arabian minority are descendants of the former slaves.
The year that the Trucial States officially abolished slavery is unclear. Some say that bondage was officially outlawed in 1963, when the Trucial rulers signed an agreement decreeing the abolition of slavery. Others say that it was in 1971, when the Trucial States joined the UN as the United Arab Emirates and accepted the UN's Conventions against slavery. However, the legislation around slavery remained unclear because the 1963 decree was never actually issued, and the UN law of 1971 was not obligatory. Slavery of people from Africa and East Asia was succeeded by the modern Kafala system of poor workers from the same region where slaves had previously been imported.
History.
Slavery and slave trade had been an issue of tension between Britain and the Gulf states since the abolition of slavery in Britain in 1833. While the British abolition of slavery never applied in the Trucial States because they were never colonies, the British fleet did oppose the Indian Ocean slave trade and prevented slave ships from Zanzibar to reach their destination in the Gulf. The British and the Trucial rulers signed treaties against the slave trade in 1839, 1847 and 1856, but the treaties was not respected in the Gulf states and British reports noted that Dubai was a big slave route for the trafficking of slaves to Saudi Arabia.
In the 1890s, the British Empire gained control over the area. They established the Trucial States in 1892. The British power over these states were managed via the India Office and their foreign policy and contact with the outside world through the Foreign Office. However, the British did not interfere with the inner policy of the Trucial States, but was content with keeping peace with the indigenous power holders, protecting British citizens, and managing the contacts between the Trucial States and the international community, in which they assured that the Trucial States obeyed the same international treaties signed by the British themselves. The British met a substantial slave trade in the area with old historic roots.
Slave trade.
Indian Ocean.
During the Omani Empire (1692–1856), Oman was a center of the Zanzibar slave trade. Slaves were trafficked from the Swahili coast of East Africa via Zanzibar to Oman. From Oman, the slaves were exported to the rest of the Arabian Peninsula and Persia, including the Trucial States, Qatar, Bahrain and Kuwait. The Omani slave trade from Africa started to shrink in the late 19th-century, but a second slave trade from Africa via Hejaz continued.
The historical records show that most slaves in the pearl industry of the Persian Gulf were shipped from either the East African Swaihili Coast or the Horn of Africa.
Hajj.
A second route of slave trade existed, with people from both Africa and East Asia, who were smuggled to Jeddah in the Arabian Peninsula in connection to the Muslim pilgrimage, "Hajj", to Mecca and Medina. These slaves were imported from the Hejaz to Oman, the Trucial States, Qatar, Bahrain and Kuwait. Victims were tricked to perform the journey willingly in the belief that they were going on the Hajj pilgrimage or employed as servants and then sold upon arrival. The method of kidnapping was also used.
India.
In 1927 a trial reveal a slave trade organization in which Indian children of both sexes were trafficked to Oman and Dubai via Persia and Gwadar.
Baluchistan.
In the 1940s, a third slave trade route was noted, in which Balochis from Balochistan were shipped across the Persian Gulf, many of whom had sold themselves or their children to escape poverty.
Ethnicity.
The vast majority of slaves were of African origin, but there were also a minority from Asia and Europe.
Of 283 female slaves who applied for manumission from their Arab owners at the British Agency in Sharjah, 151 were African (25 from Eastern Africa, 8 from Sudan, 2 from Somalia, and 126 born in Arabia by African slave parents), and of the remaining number, 46 were from Baluchistan, all of them having been captured and trafficked in their own lifetime and not born in slavery. 
Function and conditions.
Slaves were given a new name on arrival. Men's names symbolized affluence and power, and women were given vibrant names that conveyed femininity. They gradually integrated in to the local culture, gradually forgetting their past; freed slaves normally by culture stayed in the household or in a clientship of their former owners.
Female slaves were often used for sexual services as concubines for a period of time, and then sold or married off to other slaves; the slave owners would arranged both marriages and divorce for their slaves, and the offspring of two slaves would become slaves in turn.
It was common for slave owners to claim sexual services of married female slaves when the slave husband was away for long periods of time, to hunt for pearls or fish or similar labour, and sexual abuse was a common reason given when female slaves applied for manumission at the British Agency.
It was common for Arab men to use the sexual services of enslaved African women, but a male African slave who had sexual relations with a local "pure blood" Arab woman would be executed to preserve tribal honour and social status, regardless if the couple had married or not. 
Male slaves.
Male slaves where used in a number of tasks: as soldiers, pearl divers, farm labourers, cash crop workers, maritime sailors, dock workers, porters, irrigation canal workers, fishermen, and domestic servants.
In the seventeenth and eighteenth centuries European travellers frequently noted African slave soldiers and African eunuchs at the royal courts.
In the nineteenth-century, the slave trade experienced the greatest peak since the ninth-century, a thousand years earlier, because of the great growth of the pearling industry in the international world trade, which relied heavily on African slave labour.
The British urged the Trucial states not to use slave labour in the oil industries, but the Trucial rulers answered that it would be difficult to find labour to the oil industry unless slave labour was used, and the British had difficulty in controlling whether the laborers in the oil industry were slaves or free workers.
The British Foreign Office repeatedly and unsuccessfully asked the Iraq Petroleum Company not to employ slaves, but was met with the reply that it was the responsibility of the shaykhs to supply the workers.
In the 1950s, a high percentage of oil workers in Abu Dhabi were slaves.
Female slaves.
Female slaves were primarily used as either domestic servants, or as concubines (sex slaves).
The sex slave-concubines of rich urban men who had given birth to the son of their enslaver were counted as the most privileged, since they became an Umm Walad and became free upon the death of their enslaver; the concubine of a Beduoin mainly lived the same life as the rest of the tribal members and the women of the family.
Female domestic slaves lived a hard life and reproduction among slaves was low; it was noted that the infant mortality was high among slaves, and that female slaves were often raped in their childhood and rarely lived in their forties, and that poorer slave owners often prostituted them.
Black African women were primarily used as domestic house slaves rather than exclusively for sexual services, while white Caucasian women (normally Circassian or Georgian) were preferred as concubines (sex slaves), and when the main slave route of white slave girls via the Black Sea slave trade and the Kazakh Khanate slave trade was reduced after Russia's conquest of the Caucasus and Central Asia in the mid nineteenth-century, Baluchi and "Red" Ethiopian (Oromo and Sidamo) women became the preferred targets for sexual slavery. 
Non-African female slaves were sold in the Persian Gulf where they were bought for marriage; these were fewer and often Armenian, Georgian, or from Baluchistan and India.
In 1943, it was reported that Baloch girls were shipped via Oman and the Trucial States to Mecca, where they were popular as concubines, since Caucasian (Circassian) girls were no longer available, and were sold for $350–450.
The Temporary Slavery Commission (TSC) of the League of Nations in 1925 had particularly specified that concubines also had the right to freedom, but the British where particularly reluctant to enforce anti slavery legislation when it came to the harem concubines of the Muslims since they did not wish to arouse anger by interfering in such sensitive domestic issues and often avoided addressing the emancipation of slave concubines by defining the concubines as wives and thus not in fact slaves.
The number of female slaves in the Gulf was as high or higher than that of male slaves, but the number of female slaves who made applications for manumission at the British Agencies in the Gulf was significantly lower (only 280 of 950 documented cases in 1921–1946), likely because in the Islamic society of the Gulf, were women were excluded from wage labour and public life, it was impossible for a freedwoman to survive without a male protector. 
Female slaves were also given as gifts between rulers: in November 1948, for example, the ruler of Dubai gifted a number of female slaves to king Ibn Saud and his sons, receiving in return a car and 10,000 ryals.
Activism against slave trade.
1892–1950.
The British Empire, having signed the 1926 Slavery Convention as a member of the League of Nations, was obliged to fight slavery and the slave trade in all land under the direct or indirect control of the British Empire. Since the Trucial States were informally a British protectorate, the British were expected by the League of Nations to enforce this policy in the region. Officially, the British declared that they did just that, but in reality, the slavery and slave trade in the Trucial States were tolerated by the British.
As was the case with the rest of the Gulf states, the British considered their control over the region insufficient to do much about slavery and the slave trade. The British India Office advised the British authorities that any attempts to enforce an anti-slavery treaty in the region could cause economic and political unrest, since slavery was "deeply rooted in religious and political history".
The British policy was therefore to assure the League of Nations that the region followed the same anti slavery treaties signed by the British, but in parallel prevent any international observations of the area, which would disprove these claims.
The British India Office, responsible also for the Gulf region, officially reported that the British agents had anti-slavery treaties with the indigenous rulers of all the Trucial States, Muscat and Bahrain, except for Kuwait.
The British publicly burned a slave dhow in Dubai as a warning in 1928 and the shaykhs, particularly the shaykh of Qatar, expressed themselves willing to enforce the formal treaty obligations; but in reality, this was impossible, and the British reported that the indigenous authorities were "fanatical, backward, and intensely suspicious of any European interference, which they regard as a threat to their liberties".
In both 1932 and 1935, the British colonial authorities refused to interfere in the slavery of the Trucial States, Qatar, Bahrain and Kuwait, since they were afraid that they could lose control over the area if they should attempt to enforce a policy against slavery, and they therefore prevented all international observation of the area which could force them to take action.
In 1932, the official report of the India Office to the Committee of Experts on Slavery that the British agents in the Trucial states regularly participated in the manumission of slaves in the British diplomatic offices, and had managed to press down the slave trade to a minimum.
As late as 1935, the British authorities thus assured the Advisory Committee of Experts on Slavery of the League of Nations that the Trucial States, Qatar, Bahrain and Kuwait had banned all slave trading in the region in treaties with the British, while at the same time,