In the days of Peter the First, soldiers were mainly recruited from peasants' children. Young peasants were stalwart, physically well set up but they were often a poor hand at the new military wisdom. This especially concerned marching and array.
What is the most important thing in marching? To distinguish between directions.
There were no problems with the commands “Forward!” and “Back!” But it was a real torture to some soldiers to distinguish between the right and the left. It was tantalizing both for solders and corporals. Finally, a great idea entered somebody's head – to use a mediator.
A bunch of straw was attached to the right foot of a soldier and a bunch of hay was fastened to his left foot. Now everything fell into place. The corporal had not to cry aloud, “Left – right!” trying to make slack and muddle-headed soldiers march in cadence. Now he used a very simple command, “Hay – straw! Hay – straw!” It also became much easier to turn. The corporal cried, “To the hay!” and everyone turned to the left or, respectively, to the right.
These are the methods of training illiterate soldiers developed as far back as the time of Peter the Great. 
 

Collection of historical anecdotes