Somali refugees walk 200-mile miles through the desert to the Dadabb refugee camp. Those hardest to reach are in Somalia, where a quarter of the country's 7.5 million people are on the move. Shabab, a militant group linked to Al Qaeda, which controls some famine-stricken areas and is suspicious of foreign aid agencies, has blocked help. The result is streams of refugees, struggling miles through dry desert wind and fine, sleeting sand in search of sanctuary. The worst drought in decades has blistered large parts of the Horn of Africa, turning it into a hellscape of deserted villages and dead rivers. The United Nations says 12 million people need emergency aid. They are headed to the camp which holds 392,000 people, more than four times its original capacity.