Final answer:
The policy of European nations in the 1800s to expand trade networks and establish global military bases was known as imperialism.
Step-by-step explanation:
The European policy of expanding trade networks and establishing global military bases in the 1800s was known as imperialism. This policy involved extending political, economic, and military control over other nations. European powers aimed to colonize countries for various reasons, such as gaining access to raw materials, establishing new markets, and achieving military dominance over rivals.