The institution of slavery has existed for thousands and thousands of years. It predates written records and it still exists today. The Code of Hammurabi in Mesopotamia, 1800 B.C., one of the earliest written records, mentions slavery as an already established institution. While some have used the Bible, and twisted its words, to justify this wicked system, it is only within the Judeo-Christian tradition that the first and most influential reformers arose to abolish this practice. Indeed, it is in the Book of Exodus, where Moses led the Israelite slaves out of the Kingdom of Egypt, in which we hear of the first movement to free slaves. It is not until around 1000 A.D. that the first country, Hungary, led by the first Christian king, Stephen I, declared that any slave that enters the Kingdom of Hungary would be freed immediately.
The abolition of slavery was not inevitable. There are an estimated 27 million slaves worldwide today. (BBC “Millions forced into Slavery”; Kevin Bales, Disposable People, Free the Slaves). There are powerful economic reasons for this institution. Without moral leadership, even some of the most advanced ancient civilizations, the Greeks and the Romans, encouraged its growth. Now, enslavement takes place in parts of Africa, the Middle East, and South Asia. Countries deprived of Christian moral leaders (please see some below) have been slow to abolish the institution: such as Somalia in 1920, Afghanistan in 1923, Sudan and Iraq in 1924, Nepal in 1926, Iran in 1928, Burma in 1929, Morocco in the 1930s, Nigeria and Ethiopia in 1936, Qatar in 1952, Yemen in 1962, United Arab Emirates in 1963, Oman in 1970, Niger in 2003, and Mauritania in August of 2007. Even in Saudi Arabia, the spiritual home of Islam, a great moral religion, slavery was not outlawed until 1962. That means if that you could get a visa to Saudi Arabia, which is next to impossible, and you met a man or woman on the streets who was 46 or older, he or she could very well be a freed slave. This is not an ancient struggle; but a living one.

Christian Reformers:
William Wilberforce
http://en.wikipedia.org/wiki/William_Wilberforce#Conversion
Amazing Grace: William Wilberforce and the Heroic Campaign to End Slavery (1807)
Frederick Douglass
http://en.wikipedia.org/wiki/Frederick_Douglass
Narrative of the Life of Frederick Douglass, an American Slave (1845)
Booker T. Washington
http://en.wikipedia.org/wiki/Booker_T_Washington
Up From Slavery (1901)
Martin Luther King, Jr.
http://en.wikipedia.org/wiki/Martin_Luther_King%2C_Jr.
Letter from Birmingham Jail (1963)