What does the term "by echelon" refer to in the context of machine gun displacement?

The term "by echelon" refers specifically to the method of sequential leap frogging to a new position in the context of machine gun displacement. In military tactics, this involves one unit moving forward while the next unit covers or is positioned behind it. The objective is to maintain continuous fire support as units shift positions, minimizing vulnerability to enemy fire during the transition. This technique allows for a structured and coordinated movement, ensuring that the machine guns can provide suppressive fire effectively as they relocate while maintaining a defensive posture.

This approach contrasts with direct movement without gaps, simultaneous advances of all units, or retreats. Each of those methods does not facilitate the sustained protective coverage that "by echelon" provides, which is crucial in maintaining operational effectiveness when repositioning machine guns on the battlefield.