What are the two main parts of a sentence?

What type of figurative language is used in this passage from "letter from birmingham jail"? just as the prophets of the eighth century b.c. left their villages and carried their "thus saith the lord" far beyond the boundaries of their hometowns, and just as the apostle paul left his village of tarsus and carried the gospel of jesus christ to the far corners of the greco roman world, so am i compelled to carry the gospel of freedom beyond my own hometown. allusion symbolism imagery metaphor

What is the independent cause in this sentence? "if the poem is about going mad when love is lost, what would happen if love didn't die? "

What was the biggest type of pirate ship called?