Final answer:
The poem attributes the ruin of the city to the Anglo-Saxons, who invaded and settled in England after the Romans abandoned it around 400 CE.
Step-by-step explanation:
To answer the question regarding what the poem attributes the ruin of the city to, we need to consider the historical context referenced in the poem. It's important to differentiate between various invaders such as the Vikings, Romans, and Anglo-Saxons, as well as the concept of fate.
Given the context provided, it is likely that the poem refers to the period after the Romans abandoned Britain around 400 CE, which led to the Anglo-Saxons invading and settling in England. This period marked the decline of Roman influence and the rise of Anglo-Saxon domination. Therefore, in connection to Anglo-Saxon England, the poem presumably attributes the ruin of the city to the Anglo-Saxons.