What is the X in X-mas?
"on the last line of defense," 1715, attributed to William of Orange; if so, originally in a Dutch context.
We have no space to enter into the detail of the heroic struggle maintained by the young stadtholder and his faithful Dutchmen; how they laid their country under water, and successfully kept the powerful invader at bay. Once the contest seemed utterly hopeless. William was advised to compromise the matter, and yield up Holland as the conquest of Louis XIV. "No," replied he; "I mean to die in the last ditch." A speech alone sufficient to render his memory immortal. [Agnes Strickland, "Lives of the Queens of England," London, 1847]
Ultimate; final and heroic: They pumped themselves up for a last-ditch effort
[1940s+; fr earlier last-ditcher, ultimately fr die in the last ditch, ''die at the last defense line,'' found by 1715 and attributed to William of Orange]