battleline
Noun
Meaning
line of battle
The area in which one concentrates one's resources on a struggle
Source: en.wiktionary.orgExamples
The battleline between good and evil runs through the heart of every man.
Lion lost speed, causing her to fall behind the rest of the battleline, and Beatty was unable to effectively command his ships for the remainder of the engagement.
The Gary Cooper movie They Came to Cordura contains a scene of a cavalry regiment deploying from march to battleline formation.