Their journey began in war, poverty and oppression. They are fleeing, by the hundreds of thousands, from Syria, Iraq and Afghanistan, from Somalia, Iran, Pakistan and Eritrea, a ceaseless flow of humanity driven by fear, insecurity and lack of opportunity, their desperation matched only by their fortitude and sense of hope. Somehow they make it to Turkey, within sight of the Greek island of Lesbos, and embark in a flotilla of frail rubber rafts to the refuge of Europe. Entire families, old folks, young children and infants brave the perilous crossing outfitted with flimsy “life preservers” or inflated inner tubes. Most of them make it across, but some have perished at sea. Photograph by James Nachtwey for TIMERefugees, mainly Syrian, cross from Serbia into Croatia. They are among an estimated 60 million migrants on the move worldwide. Once they set foot ashore, their past lives are no more than a memory, their futures uncertain. Now they must begin walking, with whatever possessions they can carry, but they’re not sure in which direction or even where they are going. They only seem to follow those who have gone before. Eventually a system of sorts, established by various NGOs, comes into play and they begin the next leg of the journey across Europe, by boat, by train, by bus and on foot, from border to border, with a vague notion of reaching Germany or Sweden or Norway. In the Croatian town of Tovarnik, on the border with Serbia, thousands huddled at a train station and thousands more along a roadside, waiting to board trains or buses for unknown destinations. Many have no idea which country they are in. The early stages of this transition were chaotic, barely controlled, not by NGOs, but by riot police, trained to deal with civil unrest or football hooligans. Families are separated, but the police remain oblivious to their pleas, arrogant in their power over the powerless, betraying the hope of the desperate who had made it that far, against all odds, only to suffer the cruelest fate of all. James Nachtwey is a TIME contract photographer, documenting wars, conflicts and critical social issues.