Complex sentence: The poem allegorises the role of the poet as the voice of change and revolution; at the time of composing this poem, Shelley without doubt had the Peterloo Massacre of August 1819 in mind.
Split into simpler sentences: The poem allegorises the role of the poet as the voice of change and revolution. At the time of composing this poem, Shelley without doubt had the Peterloo Massacre of August 1819 in mind.