at the word of command; upon receiving the order; as soon as the order is given
Used when an action is taken immediately after a command or instruction is issued. Often appears in formal or military contexts, but can be used in organizational settings.
See also: 一下 · 命令一下 (めいれいいっか)
At the word of command, everyone started moving at once.
As soon as the order was given, the athletes lined up at the start line.