Drawn to conflict overseas
Some join terrorist groups overseas without fully understanding conflict
They see an armed conflict overseas as their own and they throw themselves into the fight.
Little do they realise the perils and complexities of the conflict.
That was the case with a Singaporean named Muhammad Ali Abd Al-Rahman.
In 2012, when bombs were dropped on Jolo island in the Philippines, 15 militants belonging to the Moro Islamic Liberation Front (MILF) were killed.
Among them was Muhammad Ali, also known by his guerrilla name, Mauwiyah.
Terrorism expert Rohan Gunaratna had described Mauwiyah as a trainer to hundreds of Philippine, Indonesian and Malaysian terrorist recruits.
Prof Gunaratna is head of the International Centre for Political Violence and Terrorism Research at the S. Rajaratnam School of International Studies in Singapore (RSIS).
Mauwiyah was not the only one to travel overseas to get involved in armed conflicts. More recently, another Singaporean, Haja Fakkurudeen Usman Ali, travelled to Syria with the intention of being a foreign fighter.
Haja, 37, a former Indian national who obtained his Singapore citizenship in 2008, had worked as supermarket manager. The Government announced his arrest last month.
Security expert Kumar Ramakrishna, also of RSIS, said: "Usually these individuals feel that their collective identity - be it ethnic, religious or nationalistic - is being attacked, although they themselves are not being attacked personally."
"These vicarious sentiments have been called moral outrage or social humiliation. They feel the need to defend their 'group tent'."
In Syria, for example, experts estimate that there are about 5,000 foreign fighters. And as of July 2013, the United Nations estimates that more than 100,000 people have been killed there, among them the foreigners fighters.
Many of these foreign fighters believe they are there to protect the innocent.
But who are the innocent ones?
Said Associate Professor Kumar: "Basically, in conflicts such as in Syria, where emotive religious divisions such as the old Sunni-Shia divide in Islam are involved, the whole situation has become extremely polarised.
"In such situations, reason and critical analysis often go missing.
"Who is innocent and who is guilty depends on which extremist narrative you happen to buy into."
In an interview published on its website in January, Public Radio International (PRI) told the story of Syrian Abu Hussein, who drove foreign fighters from Turkey into Syria.
At first, these fighters fought alongside the Free Syrian Army (FSA).
But many later joined Al-Qaeda fighters.
He said some even switched to Islamic State of Iraq and Sham (ISIS), which started as an Al-Qaeda franchise in Iraq and Syria.
ISIS is now locked in a running battle with FSA and Al-Qaeda, which has disassociated itself from ISIS.
Mr Abu Hussein told PRI: "I'm very angry because some of the guys I brought from Istanbul to Syria are now with ISIS, and ISIS is my enemy."
The dangers of joining the fight are real. Fuelled by ideology and driven to act, Abu Walid, a former bricklayer from Melbourne, Australia, left to join the conflict almost two years ago, Australian media reported.
The Australian authorities estimate that there are about 100 of their nationals in Syria.
After about nine months of making bombs and fighting, Abu Walid was killed.
Terrorism experts have described him as having had links with Anwar al-Awlaki, the Al-Qaeda leader in Yemen who was killed in 2011.
He was the man who groomed dozens of self-radicalised individuals, some of whom went on to kill and injure dozens of innocent people.
Usually these individuals feel that their collective identity - be it ethnic, religious or nationalistic - is being attacked... They feel the need to defend their 'group tent'.
- Associate Professor Kumar Ramakrishna of the RSIS, describing individuals who join terror groups overseas
Singaporeans in foreign conflicts
Since the 9/11 terrorist attacks in 2001, a few Singaporeans have immersed themselves in foreign conflicts. In some cases, they even travelled overseas to take part in terrorism-related activities. They were all later detained here. We are not naming them as some have since been rehabilitated:
Three Singaporeans were detained for receiving training and being involved with the Lashkar-e-Taiba (LeT), a terrorist group fighting at the Indian-Pakistan border.
Two were in their 20s. One of them, a university student, took his friend to Pakistan, where they were trained in bomb-making, weaponry and surveillance.
All three were arrested separately on their return.
A man in his early 20s, radicalised through online material, had sneaked into southern Thailand to link up with Thai insurgents.
He was arrested in Thailand and convicted of immigration offences for entering the country illegally.
He was later deported to Singapore and was arrested.
The former Singaporean handled the Jemaah Islamiah (JI) funds and was described as a key member.
Believed to be one of the lead planners of the plot to bomb US targets and other installations here, he allegedly funded bomb attacks in Manila in December 2000 that killed 14 people and injured 100.
He was not the only one who got involved with insurgent activities in the Mindanao region. Some others are also known to have become active members of the Moro Islamic Liberation Front (MILF).
Of Pakistani descent, the man suddenly left Singapore after the Sept 11, 2001, attacks in New York.
Suspected of having links with Al-Qaeda, he was arrested by the Northern Alliance in Afghanistan and taken to a prison in Kabul.
The man was later repatriated here.
THE SYRIAN CONFLICT BY THE NUMBERS
people who have fled the country
*people killed 4 million displaced
UNITED NATIONS FIGURES
*The death toll is believed to be slightly higher, but the UN stopped updating the figures from late January because it said the numbers could not be verified due to a lack of resources on the ground.