Jacob was appointed king over the secret combination that destroyed Nephite government around 30 AD. In the thirtieth year the chief judge was murdered upon the judgment-seat and the people divided into tribes, so that the regulations of the government were destroyed by the combination of the friends and kindreds of those who had killed the prophets (3 Nephi 7:6). This combination gathered itself together and placed Jacob at its head, calling him king over the wicked band; he was one of the chiefest who had spoken against the prophets who testified of Jesus (3 Nephi 7:9-10).
Seeing that the tribes of the people were more numerous than his band, Jacob commanded his followers to flee to the northernmost part of the land and build a kingdom there, until they should be joined by dissenters, flattering them that many would come and that they would grow strong enough to contend with the tribes. Their march was so speedy it could not be impeded; this ended the thirtieth year (3 Nephi 7:11-13).
The city inhabited by Jacob’s people was Jacobugath. At the time of Christ’s death the city was burned with fire because its wickedness was above all the wickedness of the whole earth, for its secret murders and combinations, and because its people had destroyed the peace of the Lord’s people and the government of the land; Christ himself stated the burning was so “that the blood of the prophets and the saints should not come up unto me any more against them” (3 Nephi 9:9).