issuing (an order); handing down (a command)
Used almost exclusively in the pattern 命令一下 (めいれいいっか) meaning 'as soon as the order is given' or 'upon the issuance of an order'. It is a formal, somewhat literary expression.
See also: 命令一下 (めいれいいっか)
As soon as the order was given, the unit immediately deployed.
Upon the issuance of the order, everyone took their positions.
at the word of command; upon receiving the order; as soon as the order is given
issuing of an order; command given
The term is a Sino-Japanese compound of 一 (one, once) and 下 (down, issue). The exact historical derivation is uncertain, but it follows a classical Chinese pattern where 一下 means 'once issued' or 'as soon as it is handed down'.