What is characterized by a series of engagements involving larger forces?

A series of engagements involving larger forces is best characterized as a battle. In the context of military operations, a battle typically refers to a significant armed conflict between organized, military units that can vary in size and complexity. Battles are often larger than skirmishes, which generally involve smaller forces and may not result in decisive outcomes.

While a conflict refers more broadly to any instance of fighting or contention, it does not specifically denote the scale or organization involved. A campaign, on the other hand, is a more extensive operation that encompasses multiple battles and engagements conducted over a period of time aimed at achieving strategic objectives. Thus, while campaigns include battles, the term 'battle' directly identifies a singular and specific event involving substantial military forces in direct combat, making it the most precise choice for this question.