Line of Battle
The order of troops drawn up so as to present a battle-front. There are three lines- the van, the main body, and the rear. A fleet drawn up in line of battle is so arranged that the ships are ahead and astern of each other at stated distances.
“The accuracy of the statement is contested all along the line by persons on the spot.” —W. E. Gladstone (Newspaper report).
To break the enemy's line is to derange their order of battle, and so put them to confusion.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894