How does the Marine Corps define a "Mission Essential Task List" (METL)?

The definition of a "Mission Essential Task List" (METL) in the Marine Corps is fundamentally centered around the collection of tasks that a unit must be able to perform successfully to accomplish its mission. This list is critical for operational readiness as it identifies the core capabilities and tasks essential for the unit's effectiveness in carrying out its assigned missions. The METL provides a framework for unit training and evaluation, ensuring that all personnel are prepared to perform vital functions in various operational contexts.

The other options do not align with the core concept of a METL. A checklist of equipment needed for deployment focuses on logistics rather than the tasks necessary to complete a mission. Similarly, a schedule of training exercises pertains to the planning of activities but does not encapsulate the specific essential tasks that the unit must master. A record of all completed missions documents past actions but does not define the necessary tasks required for future operational success. Thus, the key aspect of the METL is its emphasis on identifying and mastering the mission-critical tasks that are integral to a unit's readiness and effectiveness.