Which Army stability task focuses on reestablishing competent host-nation security forces?

The focus on reestablishing competent host-nation security forces falls under the category of Conduct Security Cooperation. This task involves engaging with and supporting the host-nation military and security forces to help them become effective and self-sustaining. By fostering the capability of these forces, the overall stability and security within the country can be enhanced, allowing them to take on the responsibilities of maintaining order, safeguarding their citizens, and addressing threats independently.

In the context of the other options, while they all contribute to stability operations, they do not specifically emphasize the development and reestablishment of host-nation security capabilities. Measures of Performance is about assessing the effectiveness of various actions rather than directly building force competency. Establishing Civil Security pertains to maintaining public order and safety but does not imply the training or support of local security forces. Support Law Enforcement may involve partnering with local law enforcement agencies but does not directly focus on the broader military security forces required for stability.