Turkey created an enemy: the Kurds who inhabit the mountainous region along their common border. That fact generally overrides all other considerations in Turkish-Iraqi relations. But during the Gulf war, Turkey agreed not only to shut down critical pipelines carrying Iraqi oil to market; it also allowed the United States - a NATO ally - to used Incirlik air base to mount attacks on Iraq.
Since the war, Incirlik has remained the focus of U.N. efforts to shield the Kurds of northern Iraq from Baghdad's wrath. Unfortunately for the Kurds, it has done nothing to prevent Turkey from pursuing a war of its own with Kurdish separatists it says are using Iraqi territory to mount attacks into Turkey. The Turks have engaged in regular incursions into northern Iraqi, sometimes throwing up to 30,000 troops into the country in pursuit of Kurdish rebels.
The relations between Turkey's secular government and domestic Islamists has worsened since the banning of the Welfare Party. That seems to have caused Turkey to be less enthusiastic about supporting U.S.-led military operations against Iraq. However, Ankara has not ruled out the use of the Incirlik base if air strikes do occur. Whatever its domestic problems, it has little love for Saddam Hussein and the U.S. is betting Turkey will ultimately support a military option.
Turkey involvement in Gulf War 91:
sent two frigates to the Gulf. Kept 100,000 troops and two squadrons of F- 6s on its border with Iraq. Allowed use of Incirlik Air Base for U.S. fighter planes and bombers.
Official Turkish Web site
Republic of Turkey, Ministry of Foreign Affairs