Which fire support coordination measure requires all fires to be coordinated with affected commanders prior to engagement?

The Fire Support Coordination Line (FSCL) is the correct answer because it is specifically designed to designate the boundaries within which all fire support must be coordinated with the affected commanders before engaging targets. The FSCL helps to manage and control the use of indirect fire, ensuring that all parties are aware of potential conflicts and can minimize the risk of friendly fire or collateral damage.

The purpose of the FSCL is to create a clear framework for the coordination of fire support across different units operating in the same area. When a unit identifies a target within the FSCL, it must communicate and gain approval from the respective commanders to engage, fostering cooperation and operational effectiveness.

In contrast, other measures such as the Coordinated Fire Line (CFL) and Free Fire Area (FFA) allow for different levels of engagement without the same requirement for pre-coordination with commanders. A CFL is meant to permit fire support within specified zones but still requires some coordination. An FFA allows for fires against any target without prior coordination, making it less stringent than the FSCL. A Phase Line, generally used to denote geographic lines for operational stages, does not specifically address fire coordination either. Therefore, the FSCL is the only measure among the choices that mandates this necessary coordination for