What did Monroe's assertive policy primarily involve?

Monroe's assertive policy primarily involved the removal of Native Americans west of the Mississippi River. This approach can be better understood within the context of the broader goals of the Monroe Administration, particularly concerning westward expansion and the ideology of Manifest Destiny. The idea was that American settlers had the right to expand across the continent, which often came at the expense of Native American lands and sovereignty.

During Monroe’s presidency, there was a concerted effort to negotiate treaties that would facilitate the relocation of Native American tribes to designated areas in the west. This policy aimed to open up land for European-American settlers, reflecting the prevailing belief at the time that Native American populations should be moved to make way for American expansion. The Indian Removal Act, enacted later under Andrew Jackson, was a direct continuation of these policies that were nascent during Monroe’s tenure.

In contrast, the other options do not align with the central tenets of Monroe's policy. For instance, encouraging immigration, expansion of military presence in Europe, and strengthening relations with Britain were not primary focuses of Monroe's assertive approach. Instead, those actions tie into different aspects of U.S. foreign policy and domestic agendas that were more relevant during other periods or administrations.