"A new set of strategies and tactics are needed and we need to understand why these people are radicalised ... Islamic State has very powerful ideological tools. You can't fight such groups with military and counter-terrorism measures alone."
the group.
"A considerable part of the population in Turkey does not see groups like Islamic State or Al Nusra as terror groups. This shows how they can potentially find support," said Suleyman Ozeren, a terrorism expert and head of the Ankara-based Global Policy and Strategy Institute.
FREEDOM TO TRAVEL
Murat Kipcak made no secret of his plans to go to Syria and join Islamic State, his father said, openly praising the group and socialising with others sympathetic to it. Like several other families contacted by Reuters, he said his warnings to the authorities went unheeded.
"The police say these people are going willingly and they have the freedom to travel, so it can't stop them," said a 25-year old resident of Bayrampasa, another working class Istanbul suburb, giving his name as Mehmet. He said his brother left to join Islamic State in Syria in 2013.
The brother had since returned twice and last time left for Iraq, Mehmet said, declining to give his full name because his family is part of a police investigation.
Turkey was initially a reluctant partner in the U.S.-led coalition against Islamic State, arguing there could be no end to a war threatening regional stability without the departure of Syrian President Bashar al-Assad, and advocating for his ouster.
Critics say Ankara was too ready to back hardline Islamist groups fighting Assad, contributing to the conditions which enabled Islamic State to take hold. Ankara denies such charges, saying it was quick to declare Islamic State a terrorist group and that Turkey has the most to lose from its rise.
Turkish police have been monitoring the activities of suspected low-level Islamic State militants since as early as 2013, prosecution documents seen by Reuters show.
Aaron Stein, senior fellow at the Atlantic Council, said the authorities appeared not to intervene as part of a surveillance strategy to map out the network and target its leaders.
"The lessons suggest counter-terror officials need to be far more aggressive in disrupting mid-level recruiters, working within different Turkish communities," Stein said.
Turkish officials declined to comment on intelligence operations.
In the wake of Tuesday night's attack, police have stepped up their raids on suspected safe houses. But for Mehmet, whose brother has been incommunicado since 2015, it comes too late.
"These people who become militants in Syria are the boys of our neighborhood. The police know them, where they hang out. But they say 'gathering and talking about Islam is not a crime'," Mehmet said. "And so it goes on."