Complex sentence: It is only from the 1820s that Romanticism certainly knew itself by its name, and in 1824 the Académie française took the wholly ineffective step of issuing a decree condemning it in literature.
Split into simpler sentences: It is only from the 1820s that Romanticism certainly knew itself by its name. In 1824 the Académie française took the wholly ineffective step of issuing a decree condemning it in literature.