Final answer:
The main theme is the sadness of the land caused by war, highlighted through the works of notable poets and artists who portrayed the inhumanity and suffering of war, critiqued society, and discussed its impact on personal values.
Step-by-step explanation:
The main theme of the poem about Britain and the sadness brought by war seems to best align with the sadness of the land caused by war. Poets like Wilfred Owen, Siegfried Sassoon, Rupert Brooke, and William Butler Yeats illustrated the horrific inhumanity and suffering caused by warfare in their poetry, moving away from glorification to show its true effects. Percy Bysshe Shelley, in his works 'Song to the Men of England' and 'England in 1819', addresses the exploitation of workers and displays political dissent, revealing how the expansion of British commerce and political power could ultimately lead to downfall and social suffering.
In 'England in 1819', Shelley uses metaphors to critique the various institutions in Britain, which helps sum up his message of widespread corruption and need for reform. Poets like William Wordsworth also contribute to this theme by showing how war and societal issues lead to a decay of moral values, especially evident in their impact on the poor and family affection. These explorations and criticisms were part of a larger cultural response to war, which included not only poetry but also visual arts, as seen in Käthe Kollwitz's haunting depictions of mourning and loss.