Beowulf is rightly considered to be about Beowulf, the greatest Geat hero and king. After all, the poem is framed by Beowulf's fight with and killing of, first, Grendel, and second, Grendel's mother, and then concludes with Beowulf's fight with the dragon that plagues his kingdom, and he dies protecting his people. But within this framework of heroic action is the much more complex dynastic struggles among the the Danes, the Swedes, Geats, and several other Germanic tribes.
If we were to add up the number of lines given to dynastic wars among Scandinavian tribes, including the Finnsburg Fragment, which is part of the poem but is often treated as a separate piece, we would notice to our surprise that Beowulf recounts far more than the exploits of its main character. In fact, in an important sense, Beowulf is as much about Scandinavian tribal history as it is about the deeds of a Geat leader named Beowulf. For example, very early in the poem, as Hrothgar is welcoming Beowulf to his court, Hrothgar recounts Beowulf's father's (Ecgtheow's) history:
Your father got into the greatest feud;/he handed death to Heatholaf/among the Wilfings;/then his warrior kinsman,/for dread of war, denied him shelter./Thence he sought out the South-Dane folk. . . refuge with the Scyldings. . . . (ll. 459-464)
Hrothgar is telling Beowulf about a typical Scandinavian struggle: in this case, after Beowulf's father kills a man of the Wilfing people, probably a Danish or Germanic tribe, he cannot afford to pay the wergild, compensation to the man's family, so Ecgtheow flees from his kingdom because his own people won't protect him and seeks safety with Hrothgar, a Dane. Hrothgar takes Ecgtheow in to keep him safe and, more important, pays the wergild for the death of Heatholaf, which then ends the Wilfings' attempt to kill Ecgtheow. This, as it happens, is a relatively minor example of the wars for revenge and territory that plague Scandinavia but represents a typical kind of struggle among the Danes, Swedes, Geats and other tribes, and it is important to Hrothgar that he remind Beowulf what he did for Beowulf's father.
In another episode, when Beowulf is making his report to Hygelac, his king and uncle, about the events at Hrothgar's court, Beowulf discusses another potential fight among the Danes and Swedes:
That may annoy the lord of the Heathobards,/and every warrior of that tribe,/when onto the floor he walks with his lady;/a young Danish noble, the lord's guest; on him glitter ancient heirlooms. . . . (ll. 2032-36)
This story, which essentially tells Hygelac of an incident between the Danes and the Heathobards, is important for what Beowulf does not disclose--that this potential struggle may involve the Geats in a dynastic fight between the Geats and Danes, on one hand, and the Swedes, on the other hand, a piece of news that would have been seriously helpful to Hygelac. Why Beowulf does not make the seriousness of this story clear to Hygelac is a puzzle.
In sum, then, the dynastic struggles recounted in Beowulf are often between the largest and most powerful tribes--the Danes and the Swedes--but involve the Geats because the Geats support one or the other of the tribes based on the individual circumstances. The Finnsburg Fragment (1067-1159) is considered the most complex and important of the stories about dynastic struggles in Beowulf and is often discussed as a separate piece.
The universal conflict involves the battle between good and evil, as epitomized by Beowulf fighting and defeating Grendel and his mother, which is a major part of the Beowulf epic itself. In Beowulf, Grendel and his mother are monsters who represent the forces of evil, and are linked to the Biblical Cain, murderer of his brother Abel, by him being their ancestor. This link to the Bible also represents a Christian theme in the epic, which represents the time period in which Beowulf was written, when Christianity was being adopted by the Germanic peoples. As a result, Beowulf represents the transition from paganism to Christianity, in its themes and its setting (it being set in the pre-Christian world, with Christian themes, such as the battle between good and evil, being included as part of it).