援軍

1. Origins, structure, and basic meaning

• Structure: 援軍 (えんぐん) is a noun for military reinforcements or, figuratively, additional people brought in to help.
• Basic usage: 援軍が城に到着する makes neighboring-country troops the arriving subject, while 援軍を別部署から頼む requests extra staff for a busy sales floor.

2. Common pitfalls and similar expressions

• Military reinforcement and workplace help
  • 隣国から援軍 denotes troops in a story, whereas 別の部署から援軍 figuratively denotes staff assistance. No army is dispatched to the sales floor.