This is the moment when Sandrine Koffi's dream of a new life in Europe ended - and her nightmare of an infant lost in the Macedonian night began.

As club-wielding police closed in, the 31-year-old from Cote d'Ivoire couldn't keep up with her fellow migrants, not after more than a week of treacherous hikes through mud and bone-chilling rain; of leaky tents, stolen food and fitful sleep; of loads too heavy to bear.

Koffi had given her 10-month-old daughter, Kendra, to a stronger person to carry as the 40-member group of West Africans walked with trepidation into Veles, Macedonia. They hoped, because it was pitch dark and miserably cold, that no one would see them and raise the alarm. But after a 10-day trek over 150 kilometers, their luck ran out.

Officers captured Koffi and deported her with most of the group back to Greece. Others who escaped carried Kendra all the way to the Serbian border. That was more than two weeks ago. Now, the mother cannot stop crying for her distant daughter - or wondering why they can't travel like "normal" people.

"I feel like I'm not a human being," Koffi told The Associated Press from the migrants' safe house in Greece, where she and her daughter had arrived last month in hopes of being escorted through the Balkans to Hungary and, eventually, to family in Paris. "Why is it necessary to separate a mother from her child? Why is all of this necessary?"

Each month, a tide of humanity pours through the hills of Greece, Macedonia and Serbia in the hope of entering the heart of the 28-nation European Union through its vulnerable back door in the Balkans. This is the newest of a half-dozen land and sea routes that Arab, Asian and African smugglers use to funnel migrants illegally from war zones and economic woes to opportunities in the West.

Most don't make it on their first attempt. Nor their third or fifth. Many, it seems, just keep trying - and failing - over and over.

The AP followed a group of migrants to document the challenges of the Western Balkans route, witnessing key events on the journey: the confrontations with police and locals, disagreements with the smuggler leading them and among themselves, and other difficulties.

The flow of migrants has grown from a trickle in 2012 to become the second-most popular path for illegal immigration into Europe, behind only the more dangerous option of sailing from North Africa to Italy.

Frontex, the EU agency that helps governments police the bloc's leaky frontiers, says it appears nothing will deter migrants from trying the long walk that starts in northern Greece. Their monitors have detected more than 43,000 illegal crossings on the Western Balkans route in 2014, more than double the year before.