Echelon

Echelon (French, the rung of a ladder), a method of forming troops, so called either from its appearance or because the different bodies concerned can support or replace each other, and so be used successively to attain their end. The line is broken into parts, which are moved forward successively, so that each part is parallel to the rest, but no two form part of the same line, and each has its front clear of all those in advance of it.