Last ditch effort
Final and determined attempt.
In 16th and 17th century warfare when armies were preparing the ground for a pitched battle, they would dig several lines of trenches in case they needed to retreat and regroup in prepared positions. If the men found themselves in the last ditch they had no option other than to fight where they stood or to die.
The Balloon went up
Indication of imminent trouble
Before a World War I infantry attack, artillery would soften up the target area. Before opening fire, observation balloons were sent aloft to observe and correct aim. This obviously alerted the troops in the trenches that it would not be long before they would be sent over the top to attack. So “the balloon went up” came to mean imminent trouble.
Cutting remark issued on departure.
The army of the Parthian dynasty of Persia (modern Iran) had a number of lightly equipped horse archers. They were extremely skillful and one of their tactics was to fake a retreat and then turn in their saddle and cut down pursuers with an unexpected shot. Over time, the expression has changed from “Parthian shot” to “parting shot”.
Works cited Donald, G., Wiest, A., & Shepherd, W. (2013). S”cklers, Sideburns and Bikinis: The military origins of everyday words and phrases. Bloomsbury Publishing.