Complex sentence: The naval plantations encroached on the rights of the Commoners, but the Forest gained new protection under the New Forest Act 1877, which confirmed the historic rights of the Commoners and prohibited the enclosure of more than at any time.
Split into simpler sentences: The naval plantations encroached on the rights of the Commoners, but the Forest gained new protection under an Act of Parliament in 1877. The New Forest Act 1877 confirmed the historic rights of the Commoners and prohibited the enclosure of more than at any time.