The pre-Islamic period
The main island of Bahrain (there are a total of 33 islands) is thought to have been torn from the Arabian peninsula around 6000BC. It has almost certainly been inhabited since prehistoric times.
The islands of Bahrain first stepped onto the stage of history some 3000 years BC as the centre of one of the great trading empires of the ancient world. This was the civilization of Dilmun, founded during the Bronze Age and lasting in one form or another for over 2000 years.
Dilmun developed as a centre of trade and commerce because of its location along the trade routes (pictured) linking Mesopotamia (southern Iraq) with the Indus Valley (today's India and Pakistan). And its decline dates from the time the Indus Valley civilization fell in the middle of the second millenium BC. This would of course have stripped Dilmun of its importance as a trading centre between Mesopotamia and India.
Once the decline had set in, it continued over the following centuries. There is mention of Dilmun as a vassal of Assyria in the 8th century BC and by about 600BC, it had been fully incorporated into the Assyrian empire.
Though Dilmun enjoyed considerable power and influence, it is difficult to gauge exactly how much. There is no question that at one time, Dilmun controlled a large part of the western Gulf shore (what is now eastern Saudi Arabia). But there is dispute over how far north and inland its influence was felt. At various times in its history, Dilmun probably extended as far north as Kuwait and as far inland as the oasis of Al-Hasa in modern Saudi Arabia.
There is virtually no information about what happened between Dilmun's absorption by Babylon and the arrival of Nearchus, a general in the army of Alexander the Great. He established a colony on the island of Falaika off the coast of Kuwait in the late 4th century BC. It is known that he explored the Gulf at least as far south as Bahrain. From the time of Nearchus until the coming of Islam in the 7th century AD, Bahrain was known by its Greek name of Tylos.
The six hundred years from about 300B.C. to 300A.D. seem to have been relatively prosperous ones. Writing in the first century A.D., Pliny mentioned that Tylos was famous for its pearls. During these years, Bahrain was strongly influenced and often directly ruled by various Persian civilizations; indeed, the islands were formally annexed by the Sassanian Persians in the 4th century A.D.
Interestingly, it was during the 3rd or 4th centuries A.D. that many inhabitants of Bahrain appear to have adopted the new Christian faith. It is a fact that the Nestorian sect of Christianity was well-established in Bahrain and on the Arabian side of the Gulf by the early 5th century. Church records show that Bahrain was the seat of two of the five Nestorian bishoprics existing on the Arabian side of the Gulf at the time of the arrival of Islam. It is uncertain when the two bishoprics were dissolved though they are known to have survived until 835A.D.