Which type of intelligence involves identifying adversaries' vulnerabilities to achieve strategic objectives?

The focus of the question is on identifying adversaries’ vulnerabilities to achieve strategic objectives. Operational intelligence is specifically concerned with understanding the capabilities and weaknesses of adversary forces in a way that can directly influence operations and tactics on the ground. It encompasses the analysis of information that aids in operational planning and execution, offering insights into how to effectively counter or exploit an adversary's vulnerabilities in a tactical environment.

In contrast, other types of intelligence serve different purposes. Tactical intelligence generally deals with immediate actions or short-term objectives, emphasizing real-time information that supports frontline operations rather than broader strategic planning. Strategic intelligence, on the other hand, informs long-term goals and national security policies, often involving an understanding of the larger geopolitical landscape. Field intelligence typically refers to information gathered in situ, which may not specifically focus on adversary vulnerabilities in the context of operational effectiveness.

Thus, operational intelligence is the most appropriate answer as it directly relates to the analysis and identification of adversaries' vulnerabilities with a clear aim to guide strategic objectives in border operations or similar scenarios.