The Persian Gulf is mostly shallow and has many islands, of which Bahrain is the largest. The gulf is bordered by Oman and the United Arab Emirates to the south, to the west by Qatar and Saudi Arabia, to the north by Kuwait and Iraq, and along the entire east coast by Iran. It was generally thought that the gulf had previously extended farther north and that sediment dropped by the Tigris, Euphrates, Karun, and Karkheh rivers filled the northern part of the gulf to create a great delta. But geologic investigations now indicate that the coastline has not moved and that the marshlands of the delta represent a sinking of the earth's crust as the Arabian land block pushes under Iran. The gulf waters have very slow currents and limited tidal range.
The Persian Gulf was an important transportation route in antiquity but declined with the fall of Mesopotamia. In succeeding centuries control of the region was contested by Arabs, Persians, Turks, and Western Europeans. In 1853, Britain and the Arab sheikhdoms of the Persian Gulf signed the Perpetual Maritime Truce, formalizing the temporary truces of 1820 and 1835. The sheikhs agreed to stop harassing British shipping in the Arabian Sea and to recognize Britain as the dominant power in the gulf. These sheikhdoms thus became known as the Trucial States. An international agreement among the major powers in 1907 placed the gulf in the British sphere of influence.
Although oil was discovered in the gulf in 1908, it was not until the 1930s, when major finds were made, that keen international interest in the region revived. Since World War II the gulf oil fields, among the most productive in the world, have been extensively developed, and modern port facilities have been constructed. Nearly 50% of the world's total oil reserves are estimated to be found in the Persian Gulf. It is also a large fishing source and was once the chief center of the pearling industry. In the late 1960s, following British military withdrawal from the area, the United States and the USSR sought to fill the vacuum. In 1971 the first U.S. military installation in the gulf was established at Bahrain.
The long-standing Arab-Persian conflict in the gulf, combined with the desire of neighboring states for control of large oil reserves, has led to international boundary disputes. Iraq and Iran argued over navigation rights on the Shatt al Arab, through which Iran's main ports and most productive oil fields are reached. Iran and the sheikhdom of Ras al-Khaima contested ownership of the oil-rich islands of Abu Musa and Greater and Lesser Tunb at the entrance to the gulf. Iranian forces occupied these islands in Dec., 1971, infuriating Iraq. The much-contested rights over the Shatt al Arab led Iran and Iraq into an 8-year war in the 1980s (see Iran-Iraq War). In 1984 American and other foreign oil tankers in the gulf were attacked by both Iran and Iraq. The security of Persian Gulf countries was threatened throughout this war.
When Iraq invaded Kuwait in Aug., 1990, the Persian Gulf was once again a background for conflict. International coalition ground forces were stationed in Saudi Arabia and neighboring gulf countries in the Persian Gulf War (1991). Before Iraq was expelled from Kuwait in Feb., 1991, Iraqi soldiers set fire to over 500 Kuwaiti oil wells and dumped millions of barrels of oil into the Persian Gulf, causing an environmental crisis and threatening desalination plants throughout the area. The area again was the scene of warfare in 2003 when U.S. and British forces invaded Iraq. The Persian Gulf's vast oil reserves make the area a continuing source of international tension.
The Persian Gulf was a focus of the 1980-88 Iraq-Iran War, in which each side attacked the other's oil tankers. In 1991, the Persian Gulf again was the background for what was called the Persian Gulf War or the "Gulf War" when Iraq invaded Kuwait and was subsequently pushed back, despite the fact that this conflict was primarily a land conflict.
The Persian Gulf is rich with good fishing grounds, extensive coral reefs, and abundant pearl oysters, but its ecology has come under pressure from industrialisation, and in particular, repeated petroleum spillages during recent wars.
Countries with a coastline on the Persian Gulf are (clockwise, from the north): Iran, Oman (exclave of Musandam), United Arab Emirates, Saudi Arabia, Qatar on a peninsula off the Saudi coast, Bahrain on an island, Kuwait and Iraq in the northwest. Various small islands lie within the Persian Gulf, some of which are subject to territorial disputes by the states of the region.
The oil-rich countries (excluding Iraq) that have a coastline on the Persian Gulf are referred to as the Persian Gulf States. Iraq's egress to the gulf is narrow and easily blockaded consisting of the marshy river delta of the Shatt al-Arab, which carries the waters of the Euphrates and the Tigris Rivers, where the left (East) bank is held by Iran.
In 330 B.C, the Achaemenid Empire established the first Persian Empire in Pars (Persis, or modern Fars) in the southwestern region of the Iranian plateau. Consequently in the Greek sources, the body of water that bordered this province came to be known as the Persian Gulf.
Considering the historical background of the name Persian Gulf, Sir Arnold Wilson mentions in a book, published in 1928 that:
No water channel has been so significant as Persian Gulf to the geologists, archaeologists, geographers, merchants, politicians, excursionists, and scholars whether in past or in present. This water channel which separates the Iran Plateau from the Arabia Plate, has enjoyed an Iranian Identity since at least 2200 years ago.|cquote
No written deed has remained since the era before the Persian Empire, but in the oral history and culture, the Iranians have called the southern waters: "Jam Sea", "Iran Sea", "Pars Sea".
During the years: 550 to 330 B.C. coinciding with sovereignty of the first Persian Empire on the Middle East area, especially the whole part of Persian Gulf and some parts of the Arabian Peninsula, the name of "Pars Sea" has been widely written in the compiled texts.
In the travel account of Pythagoras, several chapters are related to description of his travels accompanied by Darius the Great, to Susa and Persepolis, and the area is described. From among the writings of others in the same period, there is the inscription and engraving of Darius the great, installed at junction of waters of Arabian Gulf (Ahmar Sea = Red sea) and Nile river and Rome river (current Mediterranean) which belongs to the 5th century BC where, Darius, the king of Achaemenid Empire has named the Persian Gulf Water Channel: Pars Sea.
With the rise of Arab nationalism (Pan-Arabism) in the 1960s, some Arab states of the region started adopting the term "Arabian Gulf" (in Arabic: الخلیج العربي al-khalīj al-ʿarabī) to refer to the waterway. However, this naming has not found much acceptance outside of the Arab world, and is not recognized by the United Nations or any other international organization. The United Nations Secretariat on many occasions has requested that only "Persian Gulf" be used as the official and standard geographical designation for the body of water. Historically, "Arabian Gulf" has been a term used to indicate the Red Sea. At the same time, the historical veracity of the usage of "Persian Gulf" can be established from the works of many medieval historians.
At the Twenty-third session of the United Nations in March-April 2006, the name "Persian Gulf" was confirmed again as the legitimate and official term to be used by members of the United Nations.
Between 625 BC BC and 226 AD the northern side was dominated by the Median, Achaemenid, Seleucid and Parthian empire]]s. After the fall of the Parthian Empire, the Sassanid empire ruled the northern half and at times the southern half of the persian gulf. the Persian Gulf, along with the Silk Road was very important to trade in the Sassanid empire. Siraf was a ancient Sassanid port that was located on the north shore of the Persian Gulf in what is now the Iranian province of Bushehr.
From 1763 until 1971, the British Empire maintained varying degrees of political control over some Persian Gulf states, including the United Arab Emirates (originally called the "Trucial Coast States") and at various times Bahrain, Kuwait, Oman, and Qatar through the British Residency of the Persian Gulf.