noun
issuing of an order; command given
Refers to the act of giving an order or the moment an order is issued. Often used in formal, military, or organizational contexts.
See also: 一下
命令一下、部隊は直ちに行動を開始した。
As soon as the order was given, the unit immediately began operations.
社長の命令一下で、プロジェクトが動き出した。
With a single order from the president, the project got underway.
Compound of 命令 (order, command) and 一下 (one stroke, once; here meaning 'as soon as something is done'). The 一下 part indicates the moment the order is given.