One of my vivid recollections of my time with my father was him telling me how he fled with his family during the first Arab–Israeli war in 1948. They left in such a hurry that he did not have time to put on any shoes. Not quite able to grasp the complexity of the whole issue, I remember thinking to myself, But how was he able to run quickly enough without shoes?

My father died (in 1993) when I was 16.  Fast forward six years, when I started to work for the UN Refugee Agency, I would again come face to face with the same question: Just when and how do people decide to flee so abruptly and suddenly, leaving everything behind?

A difficult question – especially when they do everything they can at first to stay. Since the outbreak of this brutal conflict, more than 1.2 million Syrian refugees have crossed over to Jordan, Lebanon, Turkey, Iraq, Egypt and beyond. Many of them fled like my father – abruptly, suddenly – in the culmination of a process that leads them to realize that they can no longer live in denial about how dangerous and unsustainable the situation has become for them.

Remaining is what thousands of Syrians say they have tried so hard to do, even if it has meant shuttling between cities and villages back and forth over several months, taking advantage of a lull in the fighting, or a promise of a roof and some food by a distant relative.

But then comes one defining moment that triggers the realization that they have no other choice than to leave – an experience or incident that sets itself apart from all the others by its gravity and the gravity of its implication.

Three defining moments constantly appear in the narratives of refugees: Witnessing or hearing of the disappearance and killing of a person close to them, usually in a brutal manner, either in a premeditated way or through sheer indiscriminate killing; fear of the increasing reports of kidnapping (especially if the victim is perceived to be affluent and therefore to have the financial means to secure a release); or a direct and overwhelming threat to their lives or their immediate families’ lives.

Sometimes there is not one defining moment, but several that embody all of the above. This was the case of Mona, a 30-year-old Kurd I met in Iraq. Mona used to be a computer teacher in one of the schools of Hassakeh. Two months before leaving Syria, the car that was taking her and her fellow teachers to school – a trip they were used to making on a daily basis – was stopped at a checkpoint manned by one of the groups that are parties to the conflict.

The two other women in the group were ordered to get out of the car and dragged away. She never heard from them again. Rumor had it that they were killed. A couple of days later, she witnessed how the driver in the car in front of them was killed by a sniper. He died instantly. Still, as if this was not already serious enough, she did not move from her home.

Then her husband was told explicitly that he had to join an armed group or die, a gruesome reminder of the daily difficulty civilians face to stay out of the conflict. She did not think twice about the seriousness of their words. Pregnant, she went with her husband and her little boy into a neighboring country.

Mona, like so many others, had moments that induced her to make the decision to leave. But she does not think that there is any foreseeable moment defining her return. For her, there is simply no light she can see at the end of the tunnel, and that realization, she once told me, is more painful than all that she has experienced so far.

To return home was perhaps the single greatest wish my father had. It became his life’s mission to realize that goal. Unfortunately he never made it back alive, though we did manage to at least bury him in his country. I hope that Mona and millions of other Syrian refugees will be more fortunate, and that their wait in exile will be shorter.