Straddling the key straits that divide Europe and Asia, Turkey occupies a strategic position on NATO's southern flank.

The country shares borders with Greece and Bulgaria to the northwest, the Soviet Union to the northeast, Iran to the east and Syria and Iraq to the southeast. More important for NATO, however, is that Turkey controls the Bosporus, the Sea of Marmara and the Dardanelles -- collectively called the Turkish Straits -- connecting the Black Sea and the Mediterranean.

Most of the country lies in mountainous Asia Minor at the eastern end of the Mediterranean, but its largest city, Istanbul, sits mostly on the European side of the Bosporus Strait. PEOPLE

Of Turkey's population of 48.6 million, about 90 percent are ethnic Turks. The country also has a large Kurdish minority of about 3 million.

About 98 percent of the people are Moslems. Most of them adhere to the Sunni sect.

Urban areas have grown greatly since 1950 with the migration of villagers to cities, but 60 percent of Turkey's people are involved in some aspect of farming. HISTORY

Turkey enjoyed the height of its power and influence during the 600-year rule of the Ottoman Empire from the early 1300s to 1922. At its peak, the empire controlled large areas of the Middle East, southeastern Europe and North Africa, but its holdings fragmented and broke away with the rise of nationalism and the growth of European power in the 19th century. The empire collapsed after a disastrous alliance with Germany in World War I.

Turkish nationalists picked up the pieces and formed the Republic of Turkey under Kemal Ataturk in 1923. The republic concentrated on modernizing andWesternizing Turkey and instituting political and social reforms. A secular state was created.

Turkey joined the North Atlantic Treaty Organization in 1952, and U.S. air and missile bases were established on Turkish territory.

U.S.-Turkish ties cooled in 1974 when Turkey invaded Cyprus, which has a Turkish minority. The following year Turkey responded to a U.S. military aid cutoff by closing 25 U.S. military installations, but the two countries agreed to reopen the bases in 1976. ARMED FORCES

Turkey's armed forces rank as the largest in NATO after those of the United States. Total strength if 566,000 regulars, supported by 400,000 reserves and 120,000 para-military forces, according to the London-based International Institute for Strategic Studies.

About 25,000 Turkish troops are based in northern Cyprus.

The military, which has seized power twice before in 1960 and 1971, has been hard pressed recently to enforce martial law declared in December 1978 because of mounting political and sectarian violence.