The key development that facilitated imperialism in the 19th century was the advancement of technology, particularly in transportation and communication. Innovations such as steamships and the telegraph made it faster and easier for European powers to conquer and control vast territories in Africa and Asia. These technologies allowed for the rapid movement of troops, resources, and information, enabling imperial powers to establish extensive colonial empires. Additionally, industrialization fueled the demand for raw materials and new markets, motivating European nations to expand their influence globally. This technological progress played a crucial role in the expansion and maintenance of imperial rule.