What signifies the end of the preparation phase in military action?

The end of the preparation phase in military action is signified when the lead element crosses the Line of Departure (LOD) or makes contact. This is a critical moment in military operations as it marks the transition from planning and preparation to active engagement with the enemy. Crossing the LOD indicates that all necessary planning, coordination, and logistics have been completed and that the forces are now entering the operational phase where they will engage in combat.

At this point, the preparations that include troop movements, strategic positioning, and the gathering of intelligence have all culminated in a decisive action taking place. This action requires readiness from all support units, personnel, and supplies, but the crossing of the LOD specifically denotes the start of operations, making it the defining point of transitioning from preparation to execution.

In contrast, the readiness of personnel or the delivery of supplies, although essential for successful operations, do not inherently signal the completion of the preparation phase. Instead, those factors contribute to the overall operational readiness that allows for the lead element's actions at the LOD.