وَإِذَا دَخَلَ الْعَسْكَرُ فِي أَرْضِ الْحَرْبِ، فَنَوَوُا الْإِقَامَةَ خَمْسَةَ عَشَرَ يَوْمًا: لَمْ يُتِمُّوا الصَّلَاةَ.
Translation: If an army enters enemy territory and intends to stay fifteen days, it does not pray the full number of rak‘ahs.
This is a historical juristic scenario concerning the unsettled nature of a military encampment in hostile territory, not the ordinary case of settled civilian residence.