Compare the rhymes: Line - behind vs. mind - behind, and the answer is clear.
During the french attack the Russians mostly retreated, luring them into Moscow. When it was burnt, the French had no means of housing and feeding their troops and had to retreat for themselves. During their retreat no pitched battles were fought; the Russians fought in the partisan way, by a steady harrassing the French rear, flanks, and stragglers. So "in one line" seems a little far fetched.

Wilfried