European expansion episodes were mass migrations driven by population growth

Evidence

When the First Crusade reached Constantinople, one Byzantine observer wrote, it seemed like “the entire West, including all the tribes of the barbarians living beyond the Adriatic Sea to the Pillars of Hercules, had started a mass migration and was on the march, bursting forth into Asia in a solid mass, with all its belongings. In the nineteenth century spectacular population growth again produced a European eruption, generating the largest migration in history, which flowed into Muslim as well as other lands. — Samuel P. Huntington, The Clash of Civilizations and the…, 565

Categorization

• CANDY: The Byzantine observer’s image of the whole West marching into Asia is a vivid, quotable detail for casual conversation.