Complex sentence: Educated by the next generation of Caldwells who were now all abolitionists, in 1781 Kwaku Walker sued his owner for his freedom, basing his legal case upon the newly passed Massachusetts state constitution which guaranteed that all men are created free and equal.
Split into simpler sentences: Educated by the next generation of Caldwells who were then all abolitionists, in 1781 Kwaku Walker sued his owner for his freedom. He based his legal case upon the newly ratified Massachusetts state constitution (1780), which guaranteed that all men are created free and equal.