Now let me clear up why this is a fake ! At the time of Hazrat Ali the whole of Jazeeratul Arab including Yemen was under Islamic Rule. Why would a king attack a yemeni king when there was no king at that time? Even if we assume that the king was a muslim governer and a kafir attacked yemen, it would not mean that the king would try himself to gain back the land. Hazrat Ali being the Khalifah would send an army of muslims to get back the land. Teaching one dua and sitting doing nothing doesn't seem very appropriate. This is enough to open one's eyes into accepting that its non sense.