The background to 4.2 is everything that happened in Units 1, 2, & 3. The key exception: It’s Europe’s turn to join the Networks of Exchange. Using all of those cross-cultural transfers from one region to another, the Europeans had accumulated the know-how, experience, and technology to make these long distance overseas voyages a reality. The College Board calls this “Causes and Events” but don’t list any specific ones… So, focus on the European Maritime Empires and how and why they went where they did.