Noun
(military) That part of an army that is not needed to directly combat the enemy.
(military, by extension) The administrative and supply departments of an army.
Source: en.wiktionary.orgOn what came to be referred to as "Ash Wednesday", at British headquarters, rear echelon units, and the British Embassy, the British frantically burned confidential papers in anticipation of the fall of the city. Source: Internet
The American offensive began on 1 November and, after some difficulty, succeeded in destroying Japanese forces defending the Point Cruz area by 3 November, including rear echelon troops sent to reinforce Nakaguma's battered regiment. Source: Internet