Turkey's Arabian possessions comprise, besides El-Hasa on the Persian Gulf, the low-lying, hot and insalubrious Tehama and the south-western highlands (vilayets of Hejaz and Yemen) stretching continuously along the east side of the Red Sea, and including the two holy cities of Mecca and Medina.
The central zone includes Hejaz (or Hijaz), Nejd and El Hasa; much of it is a dry, stony or sandy steppe, with few wells or watering-places, and only occupied by nomad tribes; but the great wadis which intersect it contain many fertile stretches of alluvial soil, where cultivation is possible and which support a considerable settled population, with several large towns and numerous villages.
The Indian government, wishing to enter into relations with Ibrahim Pasha, as de facto ruler of Nejd and El Hasa, with a view to putting down piracy in the Persian Gulf, which was seriously affecting Indian trade, sent a small mission under Captain G.
Aeaving Riad, they passed through Yemama, and across a strip of sandy desert to El Hasa where Palgrave found himself in more congenial surroundings.
In width that forms the eastern boundary of Nejd, to reappear in the copious springs that fertilize El Hasa and the Bahrein littoral.
East of this again a succession of stony ridges running parallel to the coast has to be crossed before El Hasa is reached.
Among fruit trees the vine, apricot, peach, apple, quince, fig and banana are cultivated in the highlands, and in the lower country the date palm flourishes, particularly throughout the central zone of Arabia, in Hejaz, Nejd and El Hasa, where it is the prime article of food.
A hundred kinds of date are said to grow at Medina, of which the birni is considered the most wholesome; the halwa and the jalebi are the most delicately flavoured and sell at very high rates; the khulas of El Hasa is also much esteemed.
Other important routes leading to Nejd are those from Kuwet to Hail, and from El Hasa to Riad respectively.
In 1798 a Turkish force was sent from Bagdad into El Hasa, but was compelled to retreat without accomplishing anything, and its discomfiture added much to the renown of the Wahhabi power.
For a time it looked as if the supremacy of the Wahhabi empire was to be renewed; El Hasa, Harik, Kasim and Asir returned to their allegiance, but over Oman and Yemen Fesal never re-established his dominion, and the Bahrein sheiks with British support kept their independence.
In 1834 he was with Fesal on an expedition against El Hasa when news came of the amir's murder by his cousin Masharah.
Midhat Pasha, then governor-general, seized the occasion of asserting Turkish dominion on the Persian Gulf coast, and in 1875, in spite of British protests, occupied El Hasa and established a new province under the title of Nejd, with its headquarters at Hofuf, of which Abdallah was appointed governor.
Oman and Hasa between them occupy the eastern coast districts of Arabia to the head of the Persian Gulf.
The Oman-Hasa boundary has been usually drawn north of the promontory of El Katr.
Turkish occupation (now firmly established throughout El Hasa) includes Katif (the ancient Gerrha), and El Bidia on the coast of Katr.
Up to 1913 the Turks exercised the right of suzerainty over the maritime districts of El Hasa and Hofuf, and claimed it in Qatar and Kuwait.
In the territory controlled by the Emir of Nejd the official religion is Wahabi, but a few Shiahs are still to be found in the districts of El Hasa and Hofuf.
East of the coast of El Hasa, in the Persian Gulf, a little to the south of the port of El Katif, which, if rightly identified with the ancient Gerrha, has been celebrated throughout history as the mart of Indian trade, the starting-point of caravans across Arabia.