The Syrian conflict is also poisoning Ankara's sensitive relations with Iran, Syria's vital regional ally, and Iraq and complicating ties with Russia, undermining a declared policy of "zero problems" with neighbors.
"Syria has turned Turkey's neighborhood policy on its head," said Sinan Ülgen, a former Turkish diplomat now at the Carnegie Endowment for International Peace in Brussels. "Ankara's approach to the Syria conflict has been a radical departure from traditional Turkish caution."
Yet despite bellicose statements, political support for the Syrian opposition and growing covert aid to opposition fighters, there is little Turkey can do alone to shape the outcome.
"We will not allow a terrorist group to establish camps in northern Syria and threaten Turkey," Prime Minister Recep Tayyip Erdoğan told a news conference on July 26, referring to the Kurdistan Workers' Party (PKK), which has waged a bloody armed struggle since 1984 in southeastern Turkey. "If there is a step which needs to be taken against the terrorist group, we will definitely take this step."
It was the latest of a string of warnings that have so far had little traction on the course of a conflict that has wrong-footed Turkish diplomatic ambitions in the region.
Before the crisis, Erdoğan cultivated a friendship with President Bashar al-Assad, in stark contrast to Turkey's tense relations with the Syrian leader's father, veteran strongman Hafez al-Assad. The ruling couples even vacationed together.
After a Syrian uprising inspired by the Arab Spring pro-democracy movements in Tunisia and Egypt erupted in March 2011, Erdoğan tried to use those personal ties to persuade Assad to embrace reform and open a dialogue with the opposition.
He was rebuffed and felt slighted. From November, he began calling for the removal of Assad and Turkey helped the opposition Syrian National Council (SNC) organize on its soil.
But the Syrian leader is still there, albeit weakened. He is part of a Shiite Muslim axis spanning Iran and Iraq and his own minority Alawite sect, uncomfortable for mainly Sunni Turkey.
The faction-ridden SNC, dominated by the Muslim Brotherhood, has yet to provide a credible alternative, and international diplomacy is deadlocked and largely irrelevant for now.
"They haven't really thought this through," Gareth Jenkins, an İstanbul-based researcher on Turkish security policy, said of Turkey's leaders. "It's been 'let's get rid of Assad' without enough thought as to what comes next.
"Now their two nightmare scenarios are starting to materialize: the emergence of some form of Kurdish entity in northern Syria that would clearly be an asset to the PKK and embolden Turkish Kurds in terms of autonomy, and the Lebanonization of Syria with a long-running ethnic and confessional civil war with different groups controlling different regions," Jenkins said.
Some 45,000 Syrian refugees have poured into Turkey, straining resources and security in some border areas. With fierce fighting raging in Syria's second city, Aleppo, near the Turkish frontier, a bigger influx looms soon.
Military defectors have set up bases of the Free Syrian Army (FSA) in southern Turkey, and some are trained and coordinated by Turkish, Qatari and Saudi officers operating from a secret "nerve center" near the city of Adana, Gulf sources have told Reuters.
Foreign Islamist militants are joining the Syrian fighters crossing the border from Turkey to fight against Assad, with the apparent acquiescence of the Turkish authorities, said Fadi Hakura, a Turkey analyst at London's Chatham House think tank.
"They [Turkish officials] want to accelerate the downfall of Assad and his regime," Hakura said when asked about Ankara's attitude to such fighters. "The Turkish government feels it can control the aftermath of a post-Assad Syria."