Austere fields
Back in the first days of military aviation, all airfields would be, in today’s terms, “austere.” Just a patch of grass to park the planes along with a flat of packed earth to take off/land with tents and maybe a requisitioned chalet for the crews to bed down in.

March 19, 1916, Columbus, N.M Curtiss JN-3s of the 1st Aero Squadron. Flying from Columbus into Mexico, they accompanied Pershing on the chase for Villa. Dig the red stars.
Today, about the minimum amount of space needed to operate a modern strike aircraft starts at 3,500 feet of nice runway– and that is just for a lightly loaded aircraft.
However, the ability to use rough forward strips has long been an ace in the hole should the established bases be flattened in the first days of WWIII.
With that, check out the rough field capability of the Saab Gripen