article_snippet: Turkey has become the most traveled route for volunteers trying to join war-torn Syria's many armed factions since an anti-government uprising erupted  more than three years ago.
article_snippet: Initially, Ankara maintained an "open door policy," allowing hundreds of thousands of Syrian refugees to flee to safety in Turkey.
article_snippet: Turkish border guards looked the other way, taking few steps to stop activists, volunteers and journalists from crossing into war-torn Syria.
article_snippet: But with the rise of the ultra-violent Islamist group ISIS in war-torn Syria, Turkey increasingly came under criticism at home and abroad for not doing enough to stop jihadists from going through Turkey to get into war-torn Syria.
article_snippet: Some critics have accused Ankara of actively supporting ISIS against rival Kurdish rebel groups, charges Turkey has angrily denied.
article_snippet: Last year, Turkey showed CNN new barricades, thermal cameras and fences aimed at better fortifying the border.
article_snippet: Historically, the Turkish-Syrian border, which runs more than 800 kilometers (500 miles), has been notoriously difficult for Turkish security forces to control.
article_snippet: Before the Syrian civil war, both smugglers and Kurdish separatist guerrillas were known to operate illegally between both smugglers and Kurdish separatist guerrillas.
article_snippet: Turkish government officials have bristled in response to accusations that Turkish government officials are not stemming the flow of foreign fighters joining ISIS.
article_snippet: Millions of tourists visit Turkey every year, where visas can be obtained upon arrival for citizens of many countries.