Turkey's air strikes on Islamic State targets in Syria, and Ankara's consent to the US using a key airbase to launch attacks on the jihadists, mark a break with its previous "complacency", analysts said.
The new strategy effectively makes Turkey a full member of the US-led coalition against IS jihadists but raises the risk of cross-border reprisals and could give a stronger hand to Kurdish militants, they said.
"The Turks are in a situation where IS have become too big to ignore," Michael Stephens, head of the British Royal United Services Institute's centre in Qatar, told AFP.
"It's a political signal as much as a strategic signal."
Didier Billion from the Institute for International and Strategic Affairs in Paris said the air strikes "mean that Turkey is really joining" a coalition, of which it had only been a nominal member until now.
"Turkey has understood for months that this kind of complacency towards IS was becoming more and more dangerous, that it could blow back," he said.
Aaron Stein, a non-resident fellow at the Atlantic Council's Rafik Hariri Center for the Middle East, agreed that the military action was part of a months-long evolution in diplomatic strategy.
"Turkey had altered its rules of engagement to more clearly delineate IS as a threat to the Turkish state," he said.
Ege Seckin, an analyst at IHS Country Risk, said the IS-linked suicide bombing in the border town of Suruc on July 20 that killed 32 people "provides a convenient public justification for this policy reversal".
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Seckin said that Turkey's behaviour suggested a repositioning in the complex regional diplomacy surrounding the conflict in Syria, particularly in the wake of this month's landmark nuclear deal with Iran.
"Previously, Turkey prioritised the fight against Syrian President Assad's forces over the Islamic State. The developments in the past two days suggest that this has changed," he said.
The intervention could mean that Turkey "is seeking to secure its position in Syria" following the Iran nuclear deal that it fears could give Tehran greater scope to support Assad, he added.
- 'Contain Kurdish aspirations' -
Turkey's decision to allow the United States to use the Incirlik base gives Washington an easier jumping off point for bombing raids against IS and removes a point of tension in Turkey-US relations.
"No doubt the Turkish government decision to grant access to US military aircraft to use Incirlik in southern Turkey against Islamic State is a major turning point in Turkey's position," said Fadi Hakura from the Chatham House think tank in London.
The risk of seeing the Kurds in Syria take advantage of the new situation, however, could complicate the issue for Turkey and the police raids against IS networks in Turkey on Friday were accompanied by arrests of Kurdish militants and Marxist radicals.
Analysts also said that reports about a deal with the US to establish a no-fly zone in Syria along the Turkish border could make it easier to counter the jihadists but also to contain Kurdish forces.
"Turkey is also seeking to contain Kurdish aspirations for autonomy and to ensure its dominance over Syrian armed opposition groups," Seckin said.
In any case Hakura said, while Turkish intervention will "accelerate" the struggle against IS, "still it appears that it will take some time before the Islamic State is completely weakened".