What is defined as an "Invasion Force"?

An "Invasion Force" is best defined as a military operation characterized by extensive troop landings, typically aimed at seizing territory or engaging in combat against an enemy. This definition reflects the scale and intensity associated with an invasion, where large numbers of personnel are deployed to establish control over an area, often involving coordinated assaults on multiple points and logistics support.

The emphasis on troop landings signifies that this type of operation is not only about the movement of forces but also about the organizational and tactical strategies necessary to ensure the success of the mission against opposition forces. Such operations can include a variety of complexities, including air support, naval operations, and ground engagements, all of which contribute to the effectiveness of the invasion.

In contrast, the other provided choices refer to roles or operations that do not fit the conventional understanding of an invasion force. For instance, a small unit gathering intelligence focuses primarily on reconnaissance, while a backup support team is geared towards providing assistance rather than leading an offensive. Similarly, a relief team engaged in humanitarian missions is focused on assistance and support in non-combat scenarios, which underscores the distinct purpose and nature of an invasion force compared to these other roles.