"We miss you terribly and are extremely worried about you,” the family of Shamima Begum, 15, said in a statement.
"We understand that you have strong feelings and want to help those you believe are suffering in Syria,” they added. "You can help from home, you don't have to put yourself in danger. Please don't cross the border."
The family of Kadiz Sultana, 16, issued a similar statement: "We all love you dearly and the last four days have been a complete nightmare.”
"We would like to emphasize that we are not angry with you and you have not done anything wrong,” the family said. “We just want you all to return home, safe and sound."
Ms. Begum, Ms. Sultana, and a third girl whose family chose to withhold her name left their homes Tuesday morning and boarded a Turkish Airlines flight from Gatwick Airport to Istanbul. All three are students at London’s Bethnal Green Academy and friends with another girl who reportedly ran away to Syria in December.
The flight of the three girls has heightened concerns, especially in Europe, over the number of young people making their way to the Middle East to join a radical cause.
In September, the CIA estimated that more than 2,000 Westerners were fighting for the Islamic State in Syria – a number that has only risen since.
France has the lion’s share of European youths who have left to join one jihad or another; the last count was at about 1,000 people, most between the ages of 18 and 29, The Christian Science Monitor recently reported.
What motivates young people to leave home and fight in a foreign country?
Some have a romantic idea of war and warriors, Karim Pakzad, a research fellow at the French Institute of International and strategic relations, told The Guardian.
“There’s a certain fascination even with the head and throat-cutting,” he said.
For others, the drive is religious – these people believe that Western laws contradict Islamic teachings and are therefore immoral, the Foreign Policy Journal reported. Still others are responding to the West’s failure to end the violence and strife in Syria and other parts of the region.
All of these motivations, in turn, are fodder for the radicals and terrorists who have stepped up recruitment online. As the Monitor reported last year:
Videos distributed by radical groups, with their own YouTube accounts, flourish on the Internet. Preachers appeal to young Westerners with messages of martyrdom and loyalty packaged in rock video formats… Recruiters convince young people that they can join something bigger and forget their “little problems” back home, such as unemployment or family turmoil.
Governments and schools in the West have launched multiple efforts to counter radicalization at home.
In Austria, schools are hiring professionals to train teachers how to spot students at risk for recruitment, New York Magazine reported. Teachers are encouraged to use community resources to dissuade these students from us-versus-them ideologies and glorifying jihad.
Part of the battle is fought online. The French Army has a counter-propaganda unit of 50 or so specialists, who may be monitoring content, identifying recruiters, and publishing counterterrorism content.
Another way to prevent youths from leaving is to show them that recruiters’ promises of glory and excitement are false – especially for women.
“It is an extremely dangerous place and we have seen reports of what life is like for them and how restricted their lives become," Commander Richard Walton of London’s Counter Terrorism Command said in a statement to The Independent.
“The choice of returning home from Syria is often taken away from those under the control of Islamic State, leaving their families … devastated and with very few options to secure their safe return,” he added.