Posing as low-caste itinerant smiths selling wares, the all-black fieldworkers of the Reunited Nations team led by sociologist Dr. Homer Crawford travel the Sahara subtly subverting the culture of its nomad tribes by disseminating "progressive" Western propaganda such as the right to equality, liberty, and the pursuit of happiness with the long-term objective of leading North Africa into the modern age. Knowing the peoples they encounter may label their teachings as blasphemous, the fieldworkers attribute them to El Hassan, an imaginary leader who has incorporated the wisdom of all the sages and prophets of the world. On their way back from working at a Tuareg encampment, the fieldworkers are attacked by an Arab Union convoy trespassing on Reunited Nations territory and, in defending themselves, kill all the Arab troopers. The team then proceeds to a council of nomad tribes with the intention of arresting one of its leaders, Adb-el-Kader, for ordering raids on Reunited Nations projects, and find that Adb-el-Kader is now inciting the rest of the clans to bloody rebellion. Homer Crawford challenges Adb-el-Kader to a sword duel, disables him with a judo move, and arrests him.
Next, Crawford's team travels to Timbuktu to attend a conference with other all-black teams providing foreign aid in North Africa. There, Crawford makes a case for cooperation across teams regardless of political or national background based on the fact that all the fieldworkers are of African descent and so are deeply invested in helping to advance Africa. Some fieldworkers, including Isobel Cunningham, Jake Armstrong, and Cliff Jackson of the Africa for Africans Association (AFAA) and the British agent Rex Donaldson are in favor of such coordination. Others, including a C.I.A. operative Fred Ostrander, object strongly to it. After the meeting is adjourned, Isobel and Homer discuss the points presented at the meeting with Homer admitting that their dissemination of Western ideology will ultimately destroy the present North African cultures, but that their work must continue so that Africa does not become a liability to the world. As they take a stroll, a sniper on a minaret attempts to assassinate Homer and seemingly gets away.
Crawford's team is sent to Mopti to defuse a demonstration for El Hassan. The AFAA fieldworkers tag along to observe their tactics. On the way, Homer and Isobel are perturbed by the realization that what the fieldwork of foreign aid organizations is equivalent to the white man's destruction of indigenous cultures in North America. After the job at Mopti, Homer leaves with his second-in-command, Abe Baker, for Dakar, where Homer thwarts a second assassination attempt: this time, his brandy has been laced with cyanide. At headquarters, his team is given a new assignment: to locate the mysterious subversive El Hassan so the Reunited Nations can back him as a figure under which North Africans can unite. Unsure about how to proceed, Homer requests some time to consider the mission and confers with Abe and Isobel. Abe attempts to convince Homer that he is the natural choice to become El Hassan; he then announces he is a Party member of the Soviet Complex and that he would like Homer to secretly become one, causing Homer to realize that Abe is his would-be assassin. Once exposed, Abe attempts to kill Homer. Isobel is revealed to be a Party member of the Soviet Complex also, but she refuses to help Abe kill Homer. Homer, unwillingly, kills Abe with a karate blow to the windpipe. Isobel pledges herself to Homer as the first follower of El Hassan and is given the mission to convert Jake and Cliff to the cause.

Question: Who challenges Adb-el-Kader to a sword duel?
Answer: Homer Crawford