You will find it easier to keep track of the lectures if you use this chronological framework for orientation; I've characterised each century by its distinctive features (in practice, these don't always coincide exactly with the century; but they will help as a mnemonic device).

5th and 6th centuries: the Anglo-Saxon invasions

From AD 43 to c. AD 410 Britain was part of the Roman Empire; but in the early 5th century the Empire withdrew its military support, and over the next 2 centuries Britain was invaded and settled by pagan Germanic tribesmen from Denmark and North Germany, who drove the native population of Christianised Celts back to the North and West. 
This was part of a broader movement of Germanic tribes across Europe known as the ‘Migration period’ (4th to 6th century AD), and much of the content of Old English secular poetry is drawn from this ‘heroic age’ of the Germanic tribes.

7th century: the conversion of England

In 597 Roman missionaries sent by Pope Gregory 1 (‘Gregory the Great’) landed in Kent. Over the following century England was gradually Christianised by both Roman and Irish missionaries; the Sutton Hoo ship-grave (perhaps for Raedwald of East Anglia, d. c. 624/5) suggests the coexistence of pagan and Christian traditions.

The written culture brought by the missionaries to England was also a Latin culture. A period of relative peace and stability in the late 7th and early 8th centuries allowed the development of Latin scholarship of international status (major Latin writers included Aldhelm of Malmesbury, 640-709; Bede, 673-735; and Alcuin of York, 735-804). But we have evidence both for the survival of a Germanic tradition of secular poetry and for the development of a new religious poetry in English (see Bede's story of Caedmon).

9th century: the Viking invasions and the rise of Wessex

By the end of the 8th century monastic Latin culture was already being threatened by Viking invasions (one of the earliest raids led to the sack of the monastery at Lindisfarne in 793). During the 9th century these raids became increasingly large-scale; the Viking ‘great army’ of 865 overran Northumbria, Mercia, and East Anglia (the death of King Edmund of East Anglia at the hands of the Vikings, described by Aelfric over a century later, belongs to this period); and only Wessex under Alfred (who ruled 871-899) was able to resist the Danes successfully.

10th century: the ‘Benedictine Renaissance’ and the return of the Vikings

In the early 10th century Wessex consolidated its power over those areas of England not ruled by the Vikings, and its dialect, West Saxon, became the standard written language. Alfred had initiated a revival of learning in Wessex, accompanied by a programme of translation into English; the relative peace and political stability of the 10th century made it possible for this revival to continue, and it was assisted by the monastic reformers of the mid 10th century (Dunstan, c. 910-88; Aethelwold, bishop of Winchester 963; and Oswald, d. 992). A second wave of Viking invasions under Aethelred (who ruled 978-1016) did not succeed in destroying it; the late 10th century was a great age for book production (almost all the OE poetry we have survives in MSS of this period) and for Latin and vernacular prose (notably the English works of Aelfric (c. 955-c. 1020) and Wulfstan, archbishop of York 1002). The survival of the OE tradition of heroic poetry is attested by The Battle of Maldon, which records the death of Byrhtnoth, ealdorman of Essex, in battle against the Vikings in 991.

11th century: the end of Anglo-Saxon England

For much of the early 11th century (1016-42) England was ruled by Scandinavian kings. They were followed by native rulers; but the Norman Conquest of 1066 drove English verse and prose traditions underground to a large extent (though the Anglo-Saxon Chronicle was continued at Peterborough for almost a century after the Conquest, till 1155). English was replaced by Latin as the language of administration and record, and French as the language of courtly entertainment; and did not recover its former status until the late 14th century.