Refers to temporary military encampments or barracks, often with tents. A somewhat formal or technical term.
部隊は幕舎を設営した。
The unit set up camp.
幕舎での
Life in the barracks is harsh.
Compound of 幕 (tent, curtain) and 舎 (building, quarters). The exact historical derivation is uncertain, but the term is conventionally associated with military encampments.