The battle against terrorism has been a long and difficult one, as the country continues its struggle against Kurdish, radical Islamist, left-wing and nationalist groups that have killed tens of thousands of people over the last 30 years.

It's a battle that won't end soon. On Friday, one person was injured when a bomb exploded at a McDonald's restaurant here. Two weeks ago, a radical Marxist group claimed responsibility after an explosion killed two policeman and an Australian woman.

Left-wing and extremist religious groups have killed dozens in recent years. But by far the most devastating damage has come from Turkey's 17-year battle with the Kurdistan Workers' Party, officially listed as a foreign terrorist organization by the U.S. State Department.

An estimated 30,000 people have been killed in Turkey since 1984, when the PKK started its violent campaign for Kurdish independence. PKK operatives would typically slip into villages and kill teachers, police officers and other representatives of the Turkish central government. The long and savage war led to widespread accusations of atrocities on both sides.

Fighting has fallen off since the 1999 capture and subsequent conviction of PKK leader Abdullah Ocalan, who currently sits in jail under a death sentence that may or may not be carried out. Thousands of PKK guerrillas are said to be in the hills of Iraq and Iran, ready to resume the struggle if and when Ocalan gives the order or is executed.

Most Turks also vividly remember a period of widespread political social unrest in the late 1970s that left several thousand dead. Right-wing nationalist and Soviet-backed Marxist groups operated freely throughout the country during that time, sometimes engaging in running gun battles through city streets.

Among the terrorists was Mehmet Ali Agca, a nationalist who killed a prominent newspaper editor in Turkey before escaping the country and later trying to assassinate Pope John Paul II.

The violence ended only after a September, 1980 military coup that brought with it a period of extended martial law and gradual — if rather imperfect — return to democracy.

Turkey was also victim to a long-running Armenian terrorist campaign in the 1970s and early 1980s. Armenians assassins, nominally seeking revenge for what they charged were widespread massacres of their people by the Turks during World War I, killed a number of Turkish diplomats and others in a series of attacks around the world.

The Armenian attacks ended about the same time as the rise of the PKK, a fact that most Turks see as more than a coincidence. It was widely believed the Soviets or their clients were responsible for supplying arms and money to both the Armenians and the PKK.