Task: Question Generation
Input (English): During the Eastern Han, conscription could be avoided if one paid a commutable tax. The Eastern Han court favored the recruitment of a volunteer army. The volunteer army comprised the Southern Army (Nanjun 南軍), while the standing army stationed in and near the capital was the Northern Army (Beijun 北軍). Led by Colonels (Xiaowei 校尉), the Northern Army consisted of five regiments, each composed of several thousand soldiers. When central authority collapsed after 189 AD, wealthy landowners, members of the aristocracy/nobility, and regional military-governors relied upon their retainers to act as their own personal troops (buqu 部曲).
Output (English): What army was considered to be the volunteer army?