Crawling under barbed wire and leaping over burning tires, dozens of bare-chested young fighters train in a barren part of central Yemen, preparing to head to the front lines of their country's worsening conflict.
Less than 100 miles (150 km) away in Aden, former army officers are readying a separate contingent of volunteers to join a war that has put the energy-rich Gulf on edge.
Recruited by different factions, both units are set to fight side by side, joining a push by exiled President Abed Rabbo Mansour Hadi to create a ground force capable of regaining power from dominant Houthi fighters, who are backed by Iran.