The first fatalities among the United Arab Emirates’ mercenary army were reported last week in Yemen, where six Colombian fighters and their Australian commander were slain in combat with the Shi’ite Houthis.

Details are scant on where the incident took place, but the UAE last month was reported to have sent “hundreds” of Colombian mercenaries into Yemen to try to break a stalemated conflict between the Saudi-led forces in the south and the Shi’ites in the north.

The UAE has been building this “second army” of mercenaries, overwhelmingly from South America, since 2011. Blackwaster founder Erik Prince was initially responsible for the organization of this force, though the UAE insists he is no longer involved.

The oil-rich UAE has struggled to fill the ranks of its own military and has had success recruiting fighters from nations whose own militaries pay far less than they do. Though they initially only sent their regular troops into Yemen, rising casualties quickly convinced them to shift to the mercenaries, who are more experienced in combat and likely also viewed as more expendable by the government.